Add ability to ignore certain users comments

[thekad]

Some build/CI systems can become too noisy, you still want to pull real people's comments and ignore bot accounts when adding annotations.

[thekad]

Implementation looks fine but these options need to be documented and tested.

I'll add the test bits for github, there is no annotation testing done at all for gerrit but I can take a shot at it.

Question: Do you think it makes sense to leave these options on a per-service basis?

[ryneeverett]

I'll add the test bits for github, there is no annotation testing done at all for gerrit but I can take a shot at it.

if you can't test gerrit that's ok. Github is the critical one due to it's popularity and number of features.

Question: Do you think it makes sense to leave these options on a per-service basis?

Yes, I think we should leave them on a per-service basis. Unfortunately, it isn't a safe assumption that usernames are owned by the same entity (or in the case of bots, running the same software) across services and I don't think we should introduce that assumption here. For example, you might want to ignore a spammer who is username-squatting on one platform without ignoring the legitimate user on another platform.