chore(interfaces): move data-mysql schemas to the new format

[james-garner-canonical]

This PR replaces the pytest-interface-tester wrappers in the schema with a new convention: naming all four databags directly, as ProviderAppData, ProviderUnitData, RequirerAppData and RequirerUnitData, setting a databag that is always empty to None.

The new format is designed to be consumed by ops.Relation.load and round-trip with ops.Relation.save, so the schemas are tweaked to facilitate this -- we define custom encoders and decoders (since ops assumes JSON encoding), and add Pydantic aliases for the actual databag keys (hyphenated). Note that the __juju_encoder/decoder__ convention used here is not (yet?) supported in Ops, for now it's just designed to be consumed by the repository machinery.

A follow up PR will document this and add tooling to enforce it, after similar PRs have landed for all the other CODEOWNERS in this repository.

[sinclert-canonical]

Thanks James!

I understand this is a cross-interface effort (see GitHub search), so I will approve to have you unblocked. Worth noting: if some systematic / structure related issue is raised in any of the sibling PRs, we would ask for this interface definition to be updated as well.

In short: wait for feedback on all other PRs. If no one has anything to say, go brrrr.

[astrojuanlu]

I'm confused about versioning here, pardon my ignorance. I see this is part of mysql_client/interface/v0, but we're removing the MySQLProviderData class altogether. Shouldn't this be in a new v1?

[james-garner-canonical]

Thanks James!

I understand this is a cross-interface effort (see GitHub search), so I will approve to have you unblocked. Worth noting: if some systematic / structure related issue is raised in any of the sibling PRs, we would ask for this interface definition to be updated as well.

In short: wait for feedback on all other PRs. If no one has anything to say, go brrrr.

Thanks, I appreciate the prompt review @sinclert-canonical! The majority of reviews are in and haven't identified any unforeseen issues here, so it seems it's time for me to press the green button :)

I'm confused about versioning here, pardon my ignorance. I see this is part of mysql_client/interface/v0, but we're removing the MySQLProviderData class altogether. Shouldn't this be in a new v1?

Good question @astrojuanlu. The trick here is that these exact schema files aren't consumed from outside this repo -- legacy tooling points to charm-relation-interfaces or is pinned to an older commit on main -- and these schemas were never shipped as a versioned package. The v1 here refers to the interface's wire format and behaviour, which this update keeps intact, just adapted for a different set of tooling to consume.