I might be able to give some advice, only if by a somewhat big gotcha you are referring CAS 3.
If it is CAS 4 or 5, if it was me and I thought the docs were not enough about it, I would file an issue requesting the capability or, if ready, enhanced explain.
Could you just use throttling of failed log in attempts instead of everything else? Isn't it better for anyone? No angered users because of locked accounts, no further dev, no further doc. Trust what is already available OOTB. Tell your product owner to try to find a solution not involving custom sources nor GitHub issuing.
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