anope/atheme migration module

[slingamn]

Idea (unclear whether this proposal will work for both Anope or Atheme, or whether it needs to be specialized to one of them):

1. Support static import of all plaintext nickname and channel registration records from an existing Anope/Atheme database
2. Passwords will typically be hashed and cannot be imported directly. Instead, import the nick/account record with empty password credentials. When someone attempts to SASL PLAIN or NICKSERV IDENTIFY, and Oragono has empty password credentials for the account, check the password in a running legacy Anope/Atheme instance via its federation protocol. If it is valid, hash the password in Oragono and store it in the Oragono database.

[slingamn]

Action item: ask #atheme if there's a way to dump the opensex format as JSON.

[slingamn]

Forget federation: let's just reimplement the default Atheme password hashing algorithm and do legacy migration in-process.

[slingamn]

Initial work on this in #1301

[slingamn]

Note: this needs to preserve modelocks on the +i channel mode (and possibly others).

[slingamn]

Also channel keys if we can find them?

[slingamn]

This is done as of #1314, but likely has bugs: needs dogfooding from friendly anope / atheme operators.