CLA munger in each repository

[foxish]

Currently, the model we operate under is one instance of the mungegithub bot per repository (test-infra, contrib, kubernetes).
However, with the CNCF CLA, message posting and applying CLA labels are tied to the bot. We would need to have one instance per repository running, which doesn't seem scalable (or efficient) as we have so many different repositories.

The alternatives include:

• Separating the CLA functionality into a separate single instance of mungegithub which which can easily run on a list of repos.
• Adding the label functionality at the CNCF end.

I think the first option is reasonable. As I understand, the latter is not preferable since we want to have control of how/who we notify.
cc @kubernetes/contributor-experience @apelisse @grodrigues3

[apelisse]

As discussed, I'll take care of that (if time allows)

[foxish]

@apelisse If you put out a WIP PR, I can help with this as well, in order to speed it up.

[apelisse]

As discussed in kubernetes/test-infra#930, this will eventually be implemented in prow (please join the discussion if you have an opinion :-).

[foxish]

@apelisse Is prow ready for moving the CLA functionality into it?

[apelisse]

@foxish No, we'll just shove it in there anyway :-/

[spxtr]

I'll try to have a nice framework in place in the next couple days, then we can put it there without much hassle.

[foxish]

Thanks @spxtr