Update Agent Pools scope to Workspaces

[hs26gill]

Description

This PR updates the Agent Pools resource and data source to allow users to scope an Agent Pool to particular workspaces.

Testing plan

Covered by integration tests

External links

• go-tfe

[rhughes1]

Might be a bit of scope creep for this feature, but was thinking about if it would be possible in also having a resource dedicated to creating that link between the workspace and agent pool? ie Something like this:

resource "tfe_workspace_agent_pool" "ws" {
  agent_pool_id = "apool-123456"
  workspace_id  = "test"
}

The idea is similar to something like the workspace_variable_set resource. With this new change, we're making an assumption that the workspace(s) already exist. This doesn't automatically change the execution mode to agent for those given workspaces, this is simply a governance piece saying only these workspaces could use this agent pool.

[jbonhag]

Looking good! Added a few comments, some stuff will not pass the linter until hashicorp/go-tfe#701 gets merged.

[jbonhag]

Should this move to its own data source in order to align with the tfe_agent_pool_allowed_workspaces resource?

[hs26gill]

This resource only adds the workspace to the allowed_workspaces attribute of an agent_pool. So this was kept inside the agent_pool data source similar to the team_organization_members

[uturunku1]

Test passing 🎉