Rewrite similarity definition

[swallez]

Rewrites the index similarity definition: this is a dictionary and not a container, as users can define several similarities. The name is also user-defined, indicating a dictionary.

Also adds the boolean similarity that was missing and makes some of the configuration properties optional after inspection of the ES code base.

[github-actions]

Following you can find the validation results for the APIs you have changed.

API	Status	Request	Response
indices.add_block	🟢	2/2	2/2
indices.analyze	🟢	20/20	20/20
indices.clear_cache	🟢	4/4	4/4
indices.clone	🟢	5/5	5/5
indices.close	🟢	46/46	46/46
indices.create_data_stream	🟢	28/28	28/28
indices.create	🔴	831/843	843/843
indices.data_streams_stats	🟢	4/4	4/4
indices.delete_alias	🟢	15/15	15/15
indices.delete_data_lifecycle	⚪	Missing test	Missing test
indices.delete_data_stream	🟢	28/28	28/28
indices.delete_index_template	🟢	1/1	1/1
indices.delete_template	🟢	9/9	9/9
indices.delete	🟢	104/104	104/104
indices.disk_usage	🟢	5/5	5/5
indices.downsample	🟢	1/1	1/1
indices.exists_alias	🟢	36/36	36/36
indices.exists_index_template	⚪	Missing test	Missing test
indices.exists_template	🟢	15/15	15/15
indices.exists	🟢	39/39	39/39
indices.explain_data_lifecycle	⚪	Missing test	Missing test
indices.field_usage_stats	🟢	5/5	5/5
indices.flush	🟢	10/10	10/10
indices.forcemerge	🔴	5/5	4/5
indices.get_alias	🔴	83/83	71/83
indices.get_data_lifecycle	⚪	Missing test	Missing test
indices.get_data_stream	🔴	12/12	3/12
indices.get_field_mapping	🔴	15/15	14/15
indices.get_index_template	🔴	19/19	15/19
indices.get_mapping	🔴	91/91	87/91
indices.get_settings	🔴	56/56	54/56
indices.get_template	🟢	30/30	30/30
indices.get	🟢	53/53	53/53
indices.migrate_to_data_stream	⚪	Missing test	Missing test
indices.modify_data_stream	⚪	Missing test	Missing test
indices.open	🟢	18/18	18/18
indices.promote_data_stream	⚪	Missing test	Missing test
indices.put_alias	🟢	56/56	56/56
indices.put_data_lifecycle	⚪	Missing test	Missing test
indices.put_index_template	🔴	49/52	52/52
indices.put_mapping	🔴	73/74	74/74
indices.put_settings	🔴	54/57	57/57
indices.put_template	🔴	40/46	46/46
indices.recovery	🟢	9/9	9/9
indices.refresh	🟢	234/234	234/234
indices.reload_search_analyzers	🟢	2/2	2/2
indices.resolve_cluster	🔴	10/12	12/12
indices.resolve_index	🟢	6/6	6/6
indices.rollover	🔴	26/26	1/26
indices.segments	🔴	6/6	5/6
indices.shard_stores	🔴	5/5	4/5
indices.shrink	🟢	5/5	5/5
indices.simulate_index_template	🟢	7/7	7/7
indices.simulate_template	🔴	5/5	4/5
indices.split	🟢	11/11	11/11
indices.stats	🔴	101/101	32/100
indices.unfreeze	🟢	1/1	1/1
indices.update_aliases	🟢	22/22	22/22
indices.validate_query	🟢	7/7	7/7

You can validate these APIs yourself by using the make validate target.

[github-actions]

The backport to 7.17 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-7.17 7.17
# Navigate to the new working tree
cd .worktrees/backport-7.17
# Create a new branch
git switch --create backport-2454-to-7.17
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 7ffc441919735f1574965c7ba295be4abc03d029
# Push it to GitHub
git push --set-upstream origin backport-2454-to-7.17
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-7.17

Then, create a pull request where the base branch is 7.17 and the compare/head branch is backport-2454-to-7.17.