Add support for VNet integration

[TheRSP]

This PR closes #656 #797

The changes in this PR are as follows:

• Added route_via_vnet to WebApp and functions

I have read the contributing guidelines and have completed the following:

• Tested my code end-to-end against a live Azure subscription.
• Updated the documentation in the docs folder for the affected changes.
• Written unit tests against the modified code that I have made.
• Updated the release notes with a new entry for this PR.
• Checked the coding standards outlined in the contributions guide and ensured my code adheres to them.

If I haven't completed any of the tasks above, I include the reasons why here:

Below is a minimal example configuration that includes the new features, which can be used to deploy to Azure:

open Farmer
open Farmer.Builders

let vnet = 
    vnet {
        name $"my-vnet"

        build_address_spaces [
            addressSpace {
                space $"10.1.0.0/16"
                subnets [ 
                    subnetSpec {
                        name "workload"
                        size 18
                        add_delegations [ Network.SubnetDelegationService "Microsoft.Web/serverfarms" ]
                    }
                ]
            } 
        ]
    }

let app = webApp {
    name "my-vnet-app"
    sku Farmer.WebApp.Sku.S1
    app_insights_off
    vnet (vnet, ResourceName "workload")
}

arm {
    add_resource vnet
    add_resource app
}

[ninjarobot]

Looks great, thank you for the contribution! One small adjustment would be to follow the conventions used in other resources that attach to a subnet.

Also, IIRC there are pricing tier requirements for attaching to a vnet, so it would be good to enforce those.

[TheRSP]

Thanks for the review. I believe I have now addressed all the comments you have made.

[ninjarobot]

@TheRSP thanks for updating the operation to vnet, but also please update the docs to match. Also the behavior is still a little different in your implementation here. I cited the AKS builder before, but it might also be good to look at the VM builder for linking to managed and unmanaged resources so this can follow that same example.

[ninjarobot]

Is the Standard SKU another name for the consumption plan?

[ninjarobot]

@TheRSP can you please check into the build errors?

[TheRSP]

Sorry about that, forgot to update the tests after I enhanced the validation

[ninjarobot]

Great, thanks for the updates!

[ninjarobot]

This is released in Farmer 1.6.31.