Use of autoinstall_key_alias produces warnings when autoinstall fails schema validation

[Olivier Gayot]

When Ubuntu Advantage was rebranded as Ubuntu Pro, I introduced the "autoinstall_key_alias" as a means to provide backward compatibility for autoinstall keys.

See https://github.com/canonical/subiquity/commit/cf17de16875cb3583d8f207a58796b01bf965060

Today, when an autoinstall validation error occurs, we look through the set of top-level keys to find out what keys seem wrong. This mechanism is unaware of the autoinstall_key_alias existence so it produces warnings in presence of such keys.

subiquity/core_validation/top_level_keys: WARNING: Unrecognized top-level key 'ubuntu-advantage'
subiquity/core_validation/top_level_keys: WARNING: Unrecognized top-level keys will cause Autoinstall to throw an error in future versions.

It is not much of a problem today because only warnings are emitted. But since we want to raise errors going forward, we should make our filtering mechanism aware of the autoinstall_key_alias existence.

[Olivier Gayot (ogayot)]

Should be addressed by https://github.com/canonical/subiquity/pull/2008