Adapt to OCM spec for remote shares

[enriquepablo]

• See: Adapt to the OCM spec for remote shares #57152

Summary

This is a preliminary PR for discussion. If this goes through there are some things missing with which we'll be grateful to get some guidance:

• docs and tests
• keeping retrieved access tokens in the db
• removing tokens when removing shares (will depend on the previous point)

Also this depends on a pending PR for Guzzle:

guzzle/guzzle#3310

[enriquepablo]

Mistake breaking up the code into commits, the missing open-comment is added in a later commit:

bcf7ea1#diff-53ee4c908f9ae3a27e45d03c57ac5ed83c5916d7260561a03f279880671f6155R42

Sorry about this, I'll re-arrange a fixed pr asap.

[enriquepablo]

I'm closing this, fixing the above issue, an opening a new PR

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