Use services for determining mime type and filename

[awead]

This will ultimately relate to fixing projecthydra/sufia#2553. We interrogate an incoming object about its original name and mime type, providing a values ffor each based on some logic. Testing this was difficult when it was buried in a private method. This surfaces the methods as services which can be more easily tested, as well as exposed to other consuming applications should they wish to make use of them.

[awead]

@mjgiarlo ok, fixed it up. Incidentally, I changed DetermineMimeType to use the call/initializer strategy. Upon doing that, rubocop started complaining that Assignment Branch Condition size for determine_mime_type is too high 😠 Necessitating private methods.

[mjgiarlo]

@awead RUBOCOP. No good deed, eh? :clap:

[awead]

thanks, @mjgiarlo !