x/build/dashboard: permit specifying more than 1 builder owner

[dmitshur]

The current HostConfig allows providing the email and GitHub username of the builder owner. In many cases, there are multiple people who operate and can help with builder problems, and that information tends to be lost in old issues, mailing lists, etc.

I think it'll be better if we support entering multiple owner entries, and display those at https://farmer.golang.org/builders.

CC @golang/release.

[dmitshur]

Currently aiming for the following new internal API:

-Owner       string // optional email of owner; empty means golang-dev
-OwnerGithub string // optional GitHub username of owner
+Owners []string // owner entries (can be "github.com/{username}" or email); empty means golang-dev

With a gh helper to make the "github.com/{username}" strings a bit shorter. For example:

Owners: []string{gh("@tuxillo")},

I considered making use of the x/build/internal/gophers package, but that might be one extra step for anyone less familiar with x/build to deal with, so leaving that for later (it's not clear that it'd be better).

[dmitshur]

One way using x/build/internal/gophers helps is to be able to tell when a GitHub username and email belong to the same person, and avoid displaying/tracking both. It also helps reduce some duplication and chance of typos going unnoticed, and fewer places to update when contact info changes. So, I decided to just go ahead and use it now.

[gopherbot]

Change https://golang.org/cl/363983 mentions this issue: dashboard, cmd/coordinator: support multiple builder owners