chore: rename charms.yaml file to interface.yaml

[IronCore864]

In "overhaul to better support charmhub's interface pages", all charms.yaml are renamed to interface.yaml. Update pytest-interface-tester to load interface.yaml instead of charms.yaml.

See more discussion here.

Manual tests are done by installing this package from local path:

$ python3 run_matrix.py --include saml
Failed to load module test_requirer: No module named 'test_requirer'
INFO:root:Running tests for interface: saml
INFO:root:Running tests for version: v0
INFO:root:Running tests for role: provider
INFO:root:Running 1 saml interface tests on: ['saml-integrator']...
INFO:root:Running tests for saml
INFO:root:Running tests for charm: saml-integrator
INFO:root:Preparing testing environment for: saml-integrator
INFO:root:Cloning: saml-integrator from (https://github.com/canonical/saml-integrator-operator@main)
INFO:root:Preparing venv for /tmp/charm-relation-interfaces-tests/saml-integrator
INFO:root:Installing dependencies in venv for /tmp/charm-relation-interfaces-tests/saml-integrator
INFO:root:Installed lxml==4.9.4
ops==2.14.0
pydantic==1.10.16
signxml==3.2.2

INFO:root:Generating test file for saml at /tmp/charm-relation-interfaces-tests/saml-integrator/tests/interface
INFO:root:Running tests for /tmp/charm-relation-interfaces-tests/saml-integrator
You seem to be using pydantic v1. Please upgrade to v2, as compatibility may be dropped in a future version of pytest-interface-tester.
=================================================================== test session starts ====================================================================
platform darwin -- Python 3.11.8, pytest-8.2.2, pluggy-1.5.0
rootdir: /tmp/charm-relation-interfaces-tests/saml-integrator
configfile: pyproject.toml
plugins: interface-tester-2.0.1
collected 1 item

../../../../tmp/charm-relation-interfaces-tests/saml-integrator/tests/interface/interface_test_saml.py .                                             [100%]

==================================================================== 1 passed in 1.64s =====================================================================
INFO:root:Result: PASSED
INFO:root:Running tests for role: requirer
INFO:root:No tests specified for saml/requirer; skipping...
+++ Results +++
{
  "saml": {
    "v0": {
      "provider": {
        "saml-integrator": true
      },
      "requirer": {}
    }
  }
}

Note: We probably need to release a new version for this module but I'm not sure about the version: It's a breaking change, so by SEMVER it shouldn't be v2.0.2, although it seems "right" since it's a minor change... I left the version string in pyproject.toml unchanged, still 2.0.1 now.

[tonyandrewmeyer]

Looks good to me, although I'm not super familiar with this.

In regards to the version question, if we're not going to support both names, then a major bump seems the correct thing to do. It allows pinning to work as expected.

Note that you do need to have the version change in some way, because there's a workflow that does a release on merge to main.

[PietroPasotti]

Looks good to me.

As for the version bump, I think we're the only ones depending on this so probably we could get away with a minor bump without breaking anyone's code, but still, my personal philosophy is: versions are free. So let's give it a major bump for the sake of hygiene :)

[IronCore864]

Thanks all for the review, I have fixed the naming and bumped the version to 3.0.0 in pyproject.toml.

[IronCore864]

A gentle reminder: Could you please merge it? @PietroPasotti

I don't have permission for this repo. Thanks!

[PietroPasotti]

Sorry! was on holiday some time :)