fix: don't execute unnecessary requests for anonymous cart on initial load

[willopez]

Resolves #701
Impact: minor
Type: bugfix

Issue

1. Unnecessary requests for anonymous cart are executed when they should not. The anonymous cart query should only executed after a user has added an item to their cart.
2. An error was being returned by an api route when the user was anonymous, it should not be an error, just a flag that says that the user is anonymous.

Solution

1. Use lazyQuerys to control when cart requests are executed.
2. Return a boolean flag anonymous to denote when a user is anonymous

Breaking changes

Testing

1. Load product grid and verify no anonymousCartByCartIdQuery request are executed.
2. Add and remove items to and from the cart and verify they are add/removed as expected.
3. Complete a checkout flow and place an order
4. Verify there are no error for the api/token route

[manueldelreal]

LGTM! are we including this in the pending release branch?

[janus-reith]

I think using Lazy Query currently is the best solution.
Although the related errors in the Apollo-client repo were closed with the release of 3.0.1, multiple people still observed the described error.
I also tried upgrading apollo-client to the latest v3.0.2 and as that didnt work, also upgraded the remaining apollo packages that we're using to their latest version, also without any success.

After looking at your changes I checked out the PR locally and can confirm that the error is fixed.
Tried out anonymous carts, account carts and reconciliation, all seem to work fine.

The only minor change I'd like to suggest is the wording for refetchAccountCart / refetchCartAnonymous.

[willopez]

@manueldelreal Yes, we will include this PR in the upcoming release.

[willopez]

@janus-reith Thanks for the suggestions and testing your suggestion has been implemented.

[janus-reith]

@willopez Looks like the upcoming v3.1.2 might fix this, so we could remove that workaround again: apollographql/apollo-client#6752