Implement endpoint bindings for applications (#400)

[gboutry]

Description

The goal is to enable binding endpoints to specific spaces. This features will used in sunbeam when deploying with MAAS.

Fixes: #400

Type of change

<What type of a change is this? Please keep one or more relevant lines from below and delete the others.>

• Change existing resource
• Logic changes in resources (the API interaction with Juju has been changed)
• Change in tests (one or several tests have been changed)
• Requires a documentation update
• Maintenance work (repository related, like Github actions, or revving the Go version, etc.)

Environment

• Juju controller version: 3.4

• Terraform version: 1.6

QA steps

Manual QA steps should be done to test this PR.

• You need to have the spaces management and public associated to the model

lxc network create management-br ipv4.address=10.150.40.1/24 ipv4.nat=true ipv6.address=none ipv6.nat=false
lxc network create public-br ipv4.address=10.170.80.1/24 ipv4.nat=true ipv6.address=none ipv6.nat=false
juju add-model my-model
juju add-space management 10.150.40.0/24
juju add-space public 10.170.80.0/24

provider juju {}

data "juju_model" "resource" {
  name = "my-model"
}

resource "juju_application" "zk" {
  name  = "zookeeper"
  model = data.juju_model.resource.name

  constraints = "arch=amd64 spaces=management,public"
  charm {
    name    = "zookeeper"
    channel = "3/stable"
    base    = "[email protected]"
  }

  endpoint_bindings = [
    {
      space = "public"
    },
    {
      endpoint = "zookeeper"
      space    = "management"
    }
  ]
}

Additional notes

<Please add relevant notes & information, links to mattermost chats, other related issues/PRs, anything to help understand and QA the PR.>
Some tests were added, with a note about changing space setup when #336 is implemented.
Current integration tests have been updated to add 2 lxd bridges as support for the tests.
Tests need TEST_PUBLIC_BR and TEST_MANAGEMENT_BR containing the cidrs to be run, otherwise, they are skipped.

On behavior:
Specifying a space without an endpoint will make the space the default space (in term of bindings, not touching model configs)

Constraints are in QA/tests to make sure LXD brings the instance with right networking configuration.

[gboutry]

Force push is adding sudo in front of the 2 lxd commands creating the networks

[hmlanigan]

Thank you for the PR, it'll be a nice addition to the provider functionality.

Here are my initial comments. I haven't had the chance to run initial QA yet. Over all looks good.

I've updated the GitHub action tests, so that the 2.9 tests will work for lxd now. Please rebase as described here: https://github.com/juju/terraform-provider-juju?tab=readme-ov-file#staying-in-sync

[gboutry]

Force push is rebasing on main + adding a new commit on top of the previous ones

[gboutry]

While testing for import state, I've had multiple times the failure:

=== RUN   TestAcc_ResourceApplication_EndpointBindings
    resource_application_test.go:293: Step 2/2 error running import: ImportStateVerify attributes not equivalent. Difference is shown below. The - symbol indicates attributes missing after import.
        
          map[string]string{
        - 	"placement": "",
        + 	"placement": "0",
          }
--- FAIL: TestAcc_ResourceApplication_EndpointBindings (32.63s)

[hmlanigan]

@gboutry the placement issue you've seen in test is a known issue. there is also one with ordering of the placement values I might have a fix for.

[hmlanigan]

@gboutry I've been locally running QA on this change and found a small nit. With an application configured in a plan as such

resource "juju_application" "application_two" {
  model = data.juju_model.testmodel.name
  charm {
    name = "ubuntu"
  }
  endpoint_bindings = [
  ]
}

The first run of terraform init && terraform plan && terraform apply is good and deploys the application. However subsequent runs without changing the plan get:

Terraform will perform the following actions:

  # juju_application.application_two will be updated in-place
  ~ resource "juju_application" "application_two" {
      + endpoint_bindings = []
        id                = "six:ubuntu"
        name              = "ubuntu"
      + principal         = (known after apply)
        # (5 unchanged attributes hidden)

        # (1 unchanged block hidden)
    }

However there is no change to make. Looks good other than this.

[gboutry]

Thanks for your review @hmlanigan, I fixed this issue.

I ran manual QA steps + whole acceptance test suite on this new commit.

[hmlanigan]

LGTM. I'm sure many people will be happy with this update. Thank you!