Deal with net-ftp being unavailable

[ekohl]

In Ruby 3.0 net-ftp changed from a bundled gem to a default gem. This means it may not be available, such as when running unit tests.

Since ftp is becoming less and less common, this changes net-ftp to be an optional dependency. Users who do need ftp support should ensure the gem is installed.

[chelnak]

@ekohl Thank you 👍

[joshcooper]

The require 'net/ftp' gem should really be moved into the source_to_file method to properly handle this. Some context, if you're not using puppet generate types, then puppetserver will load types and providers and call the type's title_patterns method. Agent-side code like require 'net/ftp' needs to be guarded so it's only invoked on the agent, and not during compilation.

[chelnak]

Thanks @joshcooper .. I'll raise this with the team.