add fine-grained resource for service perimeter resource

[danawillow]

Fixes hashicorp/terraform-provider-google#4509.

In order to do this I had to make some changes to nested_query to allow it to add/remove an element of an array which is part of a nested object. I got it to work in this case by wrapping the object down the chain, so the patch request in this case would look like:

{
  "status": {
    "resources": [...]
  }
}

Notably, this doesn't merge the resources block into the status object that was returned from the API, but instead just wraps it. This works fine in this case because this API uses an update mask, so it can modify resources without changing anything else within status, but isn't future-proof if a similarly nested resource comes along that doesn't use an update mask.

Release Note Template for Downstream PRs (will be copied)

`google_access_context_manager_service_perimeter_resource`

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff
Terraform Beta: Diff

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff
Terraform Beta: Diff

[emilymye]

LGTM - some nits/small validation things

[emilymye]

Can we:

• check for array length
• leave a comment here or in nested_query saying we're reconstructing the nested patch request using the keys? I know this is partially my very undocumented code, but it's a little clearer why we are doing fun indexing that way

Also, fun ruby thing - reverse_each does the same thing as .reverse.each without copying the array (in .reverse).

[emilymye]

we can also do a reduce here if you're interested in changing this output - I think the go would look nice but the ruby ERB less nice either way! It'd be like:

wrappedObj := <%= 
  object.nested_query.keys
            .reverse[1..-1]
            .reduce("res") { |res, k| "map[string]interface{}{\n\t#{k}:#{res},\n}" }
-%>

to print out:

wrappedObj := map[string]interface{
   "k0": map[string]interface{
      "k1": ...
         "k_last": res,
      },
   },
}

[danawillow]

Done, I opted for a bit of a compromise between the two. The one with reduce looks nice for this resource but it would need some extra handling for resources with only one key, which is the majority of them.
I also didn't bother checking the array length because it seems to succeed just fine if the array is too small (the slice of the array will just be empty).

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 9 files changed, 21 insertions(+), 774 deletions(-))
Terraform Beta: Diff ( 10 files changed, 21 insertions(+), 777 deletions(-))

[danawillow]

Also the magician is wrong, my new resource does not delete 700+ lines of code. Fix for that is out for review now.