Implement gcp pubsub broker

[rsJames-ttrpg]

Description

Adding the gcppubsub broker via the gcloud-aio library

Closes #1229

Type of change

Please delete options that are not relevant.

• New feature (a non-breaking change that adds functionality)

Checklist

• My code adheres to the style guidelines of this project (just lint shows no errors)
• I have conducted a self-review of my own code
• I have made the necessary changes to the documentation
• My changes do not generate any new warnings
• I have added tests to validate the effectiveness of my fix or the functionality of my new feature
• Both new and existing unit tests pass successfully on my local environment by running just test-coverage
• I have ensured that static analysis tests are passing by running just static-analysis
• I have included code examples to illustrate the modifications

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[Lancetnik]

Hi! Looks not so bad. Which LLM model did u use?

[rsJames-ttrpg]

Hi! Looks not so bad. Which LLM model did u use?

Claude Code, mainly opus, it needs fixing though there are a couple of issues I can see after first human pass.

[Lancetnik]

We are on the road to remove all Doc usages. Please, use regular docstrings instead