[feature] Check Assignments for Similarity

/kind feature

**Describe the solution you'd like**
[A clear and concise description of what you want to happen.]

> we should avoid generating duplicate assignments, at least warning message should be logged

While some think that this check's scenario is rare. We do not decide if we need it.

**Anything else you would like to add:**
[Miscellaneous information that will assist in solving the issue.]

The issue does not name any files, tests, or entry points. First clarify how assignments should be compared, what counts as a duplicate, where assignments are generated, and the required warning behavior; done means duplicate assignments are detected and the warning is covered by tests.

Written by the indexing model from the issue text.