add ability to detect and update network tags.

[tall3n]

SUMMARY

When doing infrastructure as code it is expected that changes to code base will be reflected in the cloud platform. In this scenario changes to tags in the code base did not make its way to the cloud platform. This change rectifies this and follows the same principals as labels.

ISSUE TYPE

• Feature Pull Request

COMPONENT NAME

gcp_compute_instance

ADDITIONAL INFORMATION

Tags are currently created on instance instantiation, this fix allows network tags to be updated using gitops methodologies. For example, down the road if network tags need to be added are removed they can be done so through code.

Testing Scenario:

Existing Instance with no network tags.

1. Define Tags
2. Ensure Tags are set properly

Existing Instance with network tags.

1. Remove tags from module parameters
2. Ensure Tags are removed

New Instance

1. Create New Instance
2. Ensure Tags are set as expected.

1. Create Instance with No Tags
2. Update Tags in Code
3. Observe Tags did not change

Before:
  "tags": {
      "fingerprint": "42WmSpB8rSM="
  },

After:        
"tags": {
            "fingerprint": "s78FYhaXW7M=",
            "items": [
                "vpn"
            ]
        },

[dhendry]

@tall3n any update on this? The fact you cannot manage network tags via this module feels like its a huge problem - how do you manage firewall rules in a VPC otherwise?

Would be great to get this feature in - code changes look really minor.

cc: @rambleraptor as it looks like you are one of the main contributors here (thanks!)

[tall3n]

@dhendry

Not sure why I didn't get alerted to your comment, apologize for the late reply.

The firewall rules wasn't a huge problem as much as getting instances post creation to have their instance tags manipulated by reruns.

Because of this issue, we started using pulumi for the infrastructure as we had better full comparative diffs/updates and it fit our flexibility needs on par with ansible.

Until we made the move to using pulumi i just used this code to maintain instance tags.