Today we have multiple ways to define settings when a user needs to create a repository:

• in elasticsearch.yml file using repositories.xxx prefix where xxx is the implementation name like s3, hdfs...
• when creating the repository itself with PUT _snaphot/repo

Based on discussion we have on #22762 and on #22301 and also internally, I think we should reduce the overall complexity and completely remove support for global settings like this.

Actually, the creation of a repository is most of the time a unique manual operation so providing settings at repository creation time does not bring a lot of complexity for the end user.

And that will simplify a lot our code and our tests.

The plan would be:

• Deprecate repositories.xxx settings in 5.x:

• Azure plugin (Deprecate global repositories.azure settings #22856)
• S3 plugin (Deprecate repositories.s3 settings #23278)

• Remove repositories.xxx settings in 6.x (master branch):

• Azure plugin (Remove global repositories.azure settings #23262)
• S3 plugin ([WIP] Remove repositories.s3 settings and deprecated settings #23276 has been closed. It will be done within another PR)

• Check other plugins:

• GCS plugin (not needed as already not supported)
• HDFS plugin (not needed as already not supported)