Allow serving SRV records without "====" suffixes

[PoneyClairDeLune]

Some implementations of DNS resolver only consider [0-9a-z.-] as valid characters (e.g. Deno), and will start to throw errors if an equal sign is encountered.
Allowing serving SRV records both with and without the ==== suffix will get around such a problem.

[PoneyClairDeLune]

Truncating the ==== suffix everywhere, and only pad back when error occurs is suggested.