The original documentation was written with a focus on local storage
and missed a few important aspects of how storage types can be mixed
together in some subsystems.
* unify the susbsystem paths to be "directory" instead of using "base
path". It is not technically a directory in S3 but looks like one
and the approximation is unlikely to cause confusion.
* use S3 instead of minio where possible to emphasize the storage type
is not MinIO specific and add a section for the compatibility with
garage
* change the document structure to have two separate parts:
* [storage] the global sections
* [xxxx] the subsystem specific section
and within each of them local and S3 are documented separately
because they share nothing
* [storage] is documented to be a fallback if [xxxx] does not exist
for a given subsystem. There is no notion of inheritance because
it behaves in ways that are not tested and for which consistency is
not guaranteed
* backward compatibility with Gitea is documented to be the reason why
there are no safeguards against undocumented features
