Allow community members to run the tests in a CI

[tatiana]

Describe the bug
At the moment, pull requests created from the community fail to run the Github tests. This happened in two PRs in the last two days:

1. Fix Minor Doc & Code Issues #172
2. Use standard AWS Env Variables #176

Version

• Astro: 0.6.0

To Reproduce
Steps to reproduce the behavior:

1. Fork Astro-projects/astro
2. Create a PR from the fork into astro-projects/astro
3. See most tests failing, with messages complaining that credentials are not set, e.g.:

   File "/home/runner/work/astro/astro/.nox/test-3-8/lib/python3.8/site-packages/botocore/signers.py", line 93, in handler
    return self.sign(operation_name, request)
  File "/home/runner/work/astro/astro/.nox/test-3-8/lib/python3.8/site-packages/botocore/signers.py", line 165, in sign
    auth.add_auth(request)
  File "/home/runner/work/astro/astro/.nox/test-3-8/lib/python3.8/site-packages/botocore/auth.py", line 378, in add_auth
    raise NoCredentialsError()
botocore.exceptions.NoCredentialsError: Unable to locate credentials

https://github.com/astro-projects/astro/runs/5463617773?check_suite_focus=true

Expected behavior
Community team members should be able to fork and create PRs and see the tests passing with no secrets issues.

[tatiana]

We are in the process of refactoring our integration tests - once this is accomplished, it will be much easier to address this.

[kaxil]

There are 2 options here:

1. Only run unit tests (which is a larger work as currently not all integrations tests are marked as integration)
2. Committers (one with write access to repo) can add a certain label to the PR to mark the PR as "trusted" and hence allow the PR to run tests with secrets from the CI