Add source configuration UI

[nilmerg]

resolves #147

requires Icinga/ipl-web#214

[oxzi]

FYI, @julianbrost's comment regarding a custom certificate Common Name was now implemented in Icinga/icinga-notifications#112's commit Icinga/icinga-notifications@24a4843.

[nilmerg]

@oxzi A functional review and whether the options are correctly managed/stored is sufficient 😉

[oxzi]

Thanks! I have tested this with the current HEAD of Icinga/icinga-notifications#112 running as the backend.

I have successfully altered my existing source entry and also created a new one from scratch.

However, I realized that it is impossible to remove a source once an object was created linked to it, but this might be another day's issue:

SQLSTATE[23503]: Foreign key violation: 7 ERROR: update or delete on table "source" violates foreign key constraint "object_source_id_fkey" on table "object" DETAIL: Key (id)=(1) is still referenced from table "object".

[nilmerg]

However, I realized that it is impossible to remove a source once an object was created linked to it, but this might be another day's issue:

Yep. That's not only a problem here. Any other configuration is affected by this as well.

[oxzi]

Successfully tested the changes in the web and got the expected behavior from the icinga-notifications daemon.