Comment view_serviceable_tickets

[jjeising]

As the complexity of view_serviceable_tickets was increased in 154cee0 and b9fd435 it would probably be advisable to add some comments with an explanation for table aliases, special JOINs like epv2 and the general intent.

[a-tze]

@jjeising I think this is fixed now with #169, what do you think? Forgot to close via commit message.

[jjeising]

Yes, #169 does a good job 🎉 Thank you!