Add integ workflow, build on oldstable

[simonmarty]

Description

Why is this change being made?

1. We do not build the library on the old stable version of Go at this time. Go supports two versions concurrently.
2. We do not have a way to automatically run integration tests.

What is changing?

1. Matrix on ("stable", "oldstable") to build Go.
2. Run integration tests using a GH actions workflow.
3. Add a workflow to remove the safe-to-test label when new commits are pushed.

Related Links

• Issue #, if available:

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Testing

How was this tested?

1. Tested on fork.

When testing locally, provide testing artifact(s):

1. https://github.com/simonmarty/aws-secretsmanager-caching-go/actions/runs/23772898591
2. https://github.com/simonmarty/aws-secretsmanager-caching-go/actions/runs/23772898597

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Reviewee Checklist

Update the checklist after submitting the PR

• I have reviewed, tested and understand all changes
  If not, why:
• I have filled out the Description and Testing sections above
  If not, why:
• Build and Unit tests are passing
  If not, why:
• Unit test coverage check is passing
  If not, why:
• Integration tests pass locally
  If not, why:
• I have updated integration tests (if needed)
  If not, why:
• I have ensured no sensitive information is leaking (i.e., no logging of sensitive fields, or otherwise)
  If not, why:
• I have added explanatory comments for complex logic, new classes/methods and new tests
  If not, why:
• I have updated README/documentation (if needed)
  If not, why:
• I have clearly called out breaking changes (if any)
  If not, why:

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Reviewer Checklist

All reviewers please ensure the following are true before reviewing:

• Reviewee checklist has been accurately filled out
• Code changes align with stated purpose in description
• Test coverage adequately validates the changes

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.80%. Comparing base (5be93e0) to head (5912ea8).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #130   +/-   ##
=======================================
  Coverage   95.80%   95.80%           
=======================================
  Files           7        7           
  Lines         286      286           
=======================================
  Hits          274      274           
  Misses         10       10           
  Partials        2        2           

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