Forward arbitrary TCP traffic using aproxy

[weiiwang01]

Applicable spec:

Overview

Update the GitHub runner to allow forwarding arbitrary TCP traffic to an HTTP proxy using aproxy.

Adds two configuration options, aproxy-exclude-addresses and aproxy-redirect-ports, to filter which TCP traffic will be redirected to aproxy.

Rationale

Juju Events Changes

Module Changes

Library Changes

Checklist

• The charm style guide was applied.
• The contributing guide was applied.
• The changes are compliant with ISD054 - Managing Charm Complexity
• The documentation for charmhub is updated.
• The PR is tagged with appropriate label (urgent, trivial, complex).
• The changelog is updated with changes that affects the users of the charm.

[cbartz]

Thank you! Some comments regarding validation.

[weiiwang01]

Temporarily remove the following TCP proxy from the aproxy test in the end-to-end test suite, as the upstream proxy in the test environment is returning a 503 response. I ran the test in the PS7 environment and it worked without any problems.

          printf "" | timeout 60 nc github.com 22 | head -n 1 | grep SSH

[github-actions]

Test results for commit af5a7dc

Test coverage for af5a7dc

Wrote XML report to coverage/coverage.xml

Static code analysis report

Run started:2025-07-04 15:17:09.400785

Test results:
  No issues identified.

Code scanned:
  Total lines of code: 2050
  Total lines skipped (#nosec): 2
  Total potential issues skipped due to specifically being disabled (e.g., #nosec BXXX): 1

Run metrics:
  Total issues (by severity):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
  Total issues (by confidence):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
Files skipped (0):

[cbartz]

We have issues with the CI setup, all test passed except the test_runner_manager_openstack. I ran it locally successfully

Will force merge the PR.