Merge API response - remove summary field

[nopcoder]

This is API breaking change

Remove merge response summary as we do not reflect the actual numbers.
In case caller would like to have data about the merge, it should be reflected by calling diff after getting the new merge reference.

Close #3978

This remains a very far-reaching change. For instance: say I upgrade my lakeFS. Then my Airflow DAGs stop working!

Let's add a note to the CHANGELOG now (could be in the next PR, of course, rather than wait for whoever next releases lakeFS).

Users who use lakeFS SDK lower than v0.91.0 and verify the response will not work with this version of lakeFS as we dropped the merge summary.

[arielshaqed]

Does this break existing code? I would prefer to return junk numbers, or an arbitrary map, than do that.

If we do decide to break b/c, we will need to communicate to our users. We are one of those users, I think our Airflow provider provides merge. It mustn't break.

[nopcoder]

It will break clients with old API like other breaking changes. No existing code in lakeFS uses this response.
Will check other integrations, and give heads up before it will become part of lakeFS.

[nopcoder]

@arielshaqed created #5119 to have a version where the field is optional while the server will return a valid answer until we remove the summary field.

[github-actions]

🎊 PR Preview f37b0a8 has been successfully built and deployed to https://treeverse-lakeFS-preview-pr-5115.surge.sh

🕐 Build time: 0.027s

_{🤖 By surge-preview}

[nopcoder]

removed the use of ref as it also a package name in this code

[N-o-Z]

LGTM

[arielshaqed]

This remains a very far-reaching change. For instance: say I upgrade my lakeFS. Then my Airflow DAGs stop working!

Let's add a note to the CHANGELOG now (could be in the next PR, of course, rather than wait for whoever next releases lakeFS).

[nopcoder]

This remains a very far-reaching change. For instance: say I upgrade my lakeFS. Then my Airflow DAGs stop working!

Let's add a note to the CHANGELOG now (could be in the next PR, of course, rather than wait for whoever next releases lakeFS).

Thanks @arielshaqed!! I'll fix the client version used by Airflow before merging this one and add a note.

[nopcoder]

Update lakefs airflow provider treeverse/airflow-provider-lakeFS#66
Client SDK update wasn't required as the previous version v0.91.0 already had merge results optional.
Create and test using python client v0.91.0 merge with this branch to verify manually that we don't break.