feat: Add relation with s3 interface

[mvlassis]

Summary

• Add s3-credentials relation using the s3 interface.
• Add S3 and RelationCountGate Components.
• Add unit tests
• Add integration tests, split into 2 distinct files:
  • test_charm.py, which tests the relation with s3-integrator:s3-credentials
  • test_charm_object_storage.py, which tests the relation with minio:object-storage
• Add matrix testing for both object_storage and s3 in CI

Closes #318

[ckfbot]

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[Copilot]

Pull request overview

This PR adds support for relating argo-controller to S3 backends via the s3 interface (e.g., s3-integrator), while maintaining the existing object-storage path (e.g., MinIO), and updates tests/CI to cover both relation types.

Changes:

• Added s3-credentials relation and logic to select/configure the active storage backend (S3 vs object-storage), including optional S3 region templating.
• Split integration tests into dedicated suites for s3-integrator and minio and updated CI to run both via a matrix.
• Updated unit tests and dependency versions to support the new components.

Reviewed changes

Copilot reviewed 9 out of 12 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
charms/argo-controller/src/charm.py	Adds S3 relation component + storage selection and updates template context generation.
charms/argo-controller/metadata.yaml	Declares the new s3-credentials required endpoint.
charms/argo-controller/src/templates/minio_configmap.yaml.j2	Optionally injects S3 region into the artifact repository config.
charms/argo-controller/tests/unit/test_charm.py	Updates unit tests for optional storage relations, adds conflict-detector and endpoint parsing test.
charms/argo-controller/tests/integration/test_charm_s3.py	New integration suite covering s3-integrator:s3-credentials.
charms/argo-controller/tests/integration/test_charm_object_storage.py	New integration suite covering minio:object-storage.
charms/argo-controller/tests/integration/charms_dependencies.py	Adds S3_INTEGRATOR test dependency spec.
charms/argo-controller/tox.ini	Adds a new integration tox env and adjusts integration test targets.
charms/argo-controller/pyproject.toml	Bumps chisme version and adds a new dependency.
.github/workflows/ci.yaml	Runs both integration suites via a matrix strategy.
.gitignore	Ignores coverage.xml.

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[Copilot]

Pull request overview

Copilot reviewed 9 out of 12 changed files in this pull request and generated 2 comments.

[NohaIhab]

Thank you @mvlassis, did a first pass