## Summary
Introduces the concept of a managed agent policy. Resolves most of the acceptance criteria from elastic#76843. Remaining to be done in follow up PRs
- [x] Define hosted Agent Policy concept in Fleet.
- [x] Flag in policy? **_yes, added `is_managed: boolean`_ in agent policy SO**
- [x] Should not built only for cloud, an admin should be able to set theses restrictions.
- [x] We should have an API to configure it _**Can `POST` and `PUT` to `/api/fleet/agent_policies/{policy_id}`**_
- [x] Integration should be editable, we expect integration author to do the right thing and limit what can be edited.
- [x] Research if we can ensure the right behavior of Hosted Agent policy and restrict the super user.
- [ ] Capabilities restrictions
- [ ] An Agent enrolled in an Hosted Agent policy should not be able to be upgraded.
- [x] An Agent enrolled in an Hosted Agent policy should not be able to be unenrolled.
- [ ] No Agents cannot be enrolled into this policy by the user.
- Hide the enrollment key?
- Need to figure out the workflow.
- [x] An Agent enrolled in an Hosted Agent policy should not be able to be reassigned to a different configuration.
- [x] As a user I should be prevented to do theses action. _**No user-level checks. Only Agent Policy. No UI changes, but API errors are shown for failed actions like reassigning**_
- [x] As an API user I should receive error messages.
- [x] If making a single "flag" is easier/faster let's do it. _**Currently single `is_managed` property on agent policy SO.**_
Checks are implemented in service layer (is agent enrolled in a managed policy?)
No UI-specific changes added but UI is affected because HTTP requests (like `api/fleet/agents/{agentId}/reassign`) can fail. See screenshots below.
Tests at service (`yarn test:jest`) and http (`yarn test ftr`) layers for each of create policy, update policy, unenroll agent, and reassign agent
Bulk actions currently filter out restricted items. A follow-up PR will change them to throw an error and cause the request to fail.
## Managed Policy
Can create (`POST`) and update (`PUT`) an agent policy with an `is_managed` property. Each new saved object will have an `is_managed` property (default `false`)
<details><summary>HTTP commands</summary>
#### Create (`is_managed: false` by default)
```
curl --user elastic:changeme -X POST localhost:5601/api/fleet/agent_policies -H 'Content-Type: application/json' -d'{ "name": "User created policy", "namespace": "default"}' -H 'kbn-xsrf: true'
{"item":{"id":"edc236a0-5cbb-11eb-ab2c-0134aecb4ce8","name":"User created policy","namespace":"default","is_managed":false,"revision":1,"updated_at":"2021-01-22T14:12:58.250Z","updated_by":"elastic"}}
```
#### Create with `is_managed: true`
```
curl --user elastic:changeme -X POST localhost:5601/api/fleet/agent_policies -H 'Content-Type: application/json' -d'{ "name": "User created policy", "namespace": "default"}' -H 'kbn-xsrf: true'
{"item":{"id":"67c785b0-662e-11eb-bf6b-4790dc0178c0","name":"User created policy","namespace":"default","is_managed":false,"revision":1,"updated_at":"2021-02-03T14:45:06.059Z","updated_by":"elastic"}}
```
#### Update with `is_managed: true`
```
curl --user elastic:changeme -X PUT -H 'Content-Type: application/json' -H 'kbn-xsrf: 1234' localhost:5601/api/fleet/agent_policies/67c785b0-662e-11eb-bf6b-4790dc0178c0 -d '{ "name":"User created policy","namespace":"default","is_managed":true }'
{"item":{"id":"67c785b0-662e-11eb-bf6b-4790dc0178c0","name":"User created policy","namespace":"default","is_managed":true,"revision":2,"updated_at":"2021-02-03T14:47:28.471Z","updated_by":"elastic","package_policies":[]}}
```
</details>
## Enroll behavior
is not changed/addressed in this PR. Agents can still be enrolled in managed policies
## Unenroll Agent from managed policy behavior
#### Enrolled in managed agent policy, cannot be unenrolled
```
curl --user elastic:changeme -X POST http://localhost:5601/api/fleet/agents/441d4a40-6710-11eb-8f57-db14e8e41cff/unenroll -H 'kbn-xsrf: 1234' | jq
{
"statusCode": 400,
"error": "Bad Request",
"message": "Cannot unenroll 441d4a40-6710-11eb-8f57-db14e8e41cff from a managed agent policy af9b4970-6701-11eb-b55a-899b78cb64da"
}
```
<details><summary>Screenshots for managed & unmanaged policies</summary>
#### Enrolled in managed agent policy, cannot be unenrolled
<img width="1931" alt="Screen Shot 2021-01-19 at 1 22 53 PM" src="https://user-images.githubusercontent.com/57655/105081614-67d05980-5a60-11eb-8faa-07e4e722a5b5.png">
<img width="1199" alt="Screen Shot 2021-01-19 at 1 30 26 PM" src="https://user-images.githubusercontent.com/57655/105081617-67d05980-5a60-11eb-9099-832dc6e04eca.png">
<img width="1971" alt="Screen Shot 2021-01-19 at 1 30 42 PM" src="https://user-images.githubusercontent.com/57655/105081618-67d05980-5a60-11eb-9a84-b80b6295ba19.png">
#### Enrolled agent policy is not managed, agent can be unenrolled<img width="1917" alt="Screen Shot 2021-01-19 at 1 44 12 PM" src="https://user-images.githubusercontent.com/57655/105081951-e3caa180-5a60-11eb-9308-7741b8986e8e.png">
<img width="2183" alt="Screen Shot 2021-01-19 at 1 44 19 PM" src="https://user-images.githubusercontent.com/57655/105081952-e3caa180-5a60-11eb-9833-1c721be0a107.png">
</details>
## Reassign agent
#### No agent can be reassigned to a managed policy
```
curl --user elastic:changeme -X 'PUT' 'http://localhost:5601/api/fleet/agents/482760d0-6710-11eb-8f57-db14e8e41cff/reassign' -H 'kbn-xsrf: xxx' -H 'Content-Type: application/json' -d '{"policy_id":"af9b4970-6701-11eb-b55a-899b78cb64da"}'
{
"statusCode": 400,
"error": "Bad Request",
"message": "Cannot reassign an agent to managed agent policy 94129590-6707-11eb-b55a-899b78cb64da"
}
```
<details><summary>Screenshots</summary>
<img width="1350" alt="Screen Shot 2021-02-04 at 2 14 51 PM" src="https://user-images.githubusercontent.com/57655/106943490-8044a300-66f3-11eb-9d2c-4b1ceef2e783.png">
</details>
#### Enrolled in managed agent policy, cannot be reassigned
```
curl --user elastic:changeme -X 'PUT' 'http://localhost:5601/api/fleet/agents/482760d0-6710-11eb-8f57-db14e8e41cff/reassign' -H 'kbn-xsrf: xxx' -H 'Content-Type: application/json' -d '{"policy_id":"af9b4970-6701-11eb-b55a-899b78cb64da"}'
{
"statusCode": 400,
"error": "Bad Request",
"message": "Cannot reassign an agent from managed agent policy 94129590-6707-11eb-b55a-899b78cb64da"
}
```
<details><summary>Screenshots</summary>
<img width="1364" alt="Screen Shot 2021-01-19 at 2 58 38 PM" src="https://user-images.githubusercontent.com/57655/105086737-72dab800-5a67-11eb-8f5e-93cd7768b914.png">
<img width="1367" alt="Screen Shot 2021-01-19 at 2 58 44 PM" src="https://user-images.githubusercontent.com/57655/105086740-73734e80-5a67-11eb-8ef9-9c7005a0a4ea.png">
<img width="623" alt="Screen Shot 2021-01-19 at 2 59 27 PM" src="https://user-images.githubusercontent.com/57655/105086741-740be500-5a67-11eb-8fc2-721f8b5d178a.png">
</details>
#### Enrolled agent policy is unmanaged, agent can be reassigned to another unmanaged policy
<details><summary>Screenshots</summary>
<img width="1368" alt="Screen Shot 2021-01-19 at 3 00 01 PM" src="https://user-images.githubusercontent.com/57655/105086754-78d09900-5a67-11eb-86a5-9e3ac02d6e1f.png">
<img width="1363" alt="Screen Shot 2021-01-19 at 3 00 08 PM" src="https://user-images.githubusercontent.com/57655/105086761-7a01c600-5a67-11eb-991d-acf994e2a393.png">
<img width="625" alt="Screen Shot 2021-01-19 at 3 00 46 PM" src="https://user-images.githubusercontent.com/57655/105086764-7a9a5c80-5a67-11eb-8290-e79648d01579.png">
</details>
### Checklist
Delete any items that are not applicable to this PR.
- [ ] Any text added follows [EUI's writing guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses sentence case text and includes [i18n support](https://github.com/elastic/kibana/blob/master/packages/kbn-i18n/README.md)
- [ ] [Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html) was added for features that require explanation or tutorials
- [x] [Unit or functional tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html) were updated or added to match the most common scenarios
