Implement OpenSearch core branching strategy

[prudhvigodithi]

Description

Ensure MAJOR_VERSION.x branch exists, the main branch acts as source of truth effectively working on 2 versions at the same time.

Related META issue

opensearch-project/opensearch-plugins#142

Current Behavior

Currently plugins follow a branching strategy where they work on main for the next development iteration, effectively working on 2 versions at the same time. This is not always true for all plugins, the release branch or branch pattern is not consistent, the lack of this standardization would limit multiple automation workflows and alignment with core repo. More details on META ISSUE

Proposed solution

Follow OpenSearch core branching. Create 1.x and 2.x branches, do not create 2.0 as a branch of main, instead create main -> 2.x -> 2.0. Maintain working CI for 3 releases at any given time.

[peternied]

This has already been adopted for this repository, what is the intended action of this issue?

[prudhvigodithi]

Hey @peternied if Core branching is already adopted to security, we can close this issue.

[dblock]

Could we please double-check that:

• main is building 3.0
• 2.x is building next 2.x, which is currently 2.4.0
• 2.3 is building next 2.3, which is 2.3.1
• manifests in https://github.com/opensearch-project/opensearch-build/tree/main/manifests include all 3

[peternied]

Keeping this open until the final checklist has been completed

[stephen-crawford]

I will look at this as well @scrawfor99

[stephen-crawford]

@peternied, main is building 3.0.0; 2.x is building 2.4.0; and 2.3 is building 2.3.1 so the backend is all set!