notifier: add ServerName configuration for TLS

[jzelinskie]

No description provided.

[Quentin-M]

You changed the generic utility function loadTLSClientConfig to make it specific to the HTTP Notifier. True it is not used by anything else at the moment, but it may be. Also, almost none of the functions in the utility package are re-used at that point (ie. LoadTLSClientConfigForServer, the sibling function is just used in the API as well) - but they are pretty generic imho and could be re-used at some point.

[jzelinskie]

True it is not used by anything else at the moment, but it may be.

This is a good reason why we should wait and see if it can be reused before refactoring it out. If it can, refactor it out; if it can't, keep it local to the thing using it. The reason I made it localized was because if we continue adding new options for the TLS config, the parameters to the function could get huge. To handle this problem you can do a number of things:

• Make the function specific to *config.NotifierConfig
• Make the function specific to a new *config.TLSConfig
• Make the function take a *tls.Config instead of allocating our own inside the function

I chose the least-invasive option.

[Quentin-M]

Sounds good to me.
Should we do the same thing with LoadTLSClientConfigForServer then?

[Quentin-M]

LGTM