`has_s2r` and `has_r2s` always false for aliases

[scossu]

The /languages endpoint always shows false values for has_s2r and has_r2s . This is because aliases don't have their own table, and the function that sets the values has_s2r and has_r2s is not accounting for that redirection.

There are two options to solve this:

1. add the alias_of key to aliases, pointing to the language that the entry is an alias of. This is more transparent in regard to the entry being an alias, and also easier to maintain because it requires no other coordination; however it requires changes to the API client which needs to perform another lookup in the JSON structure to find further metadata for the actual table.
2. Copy relevant metadata from the actual table to the alias. This maintains consistency of behavior, but it duplicates data and may require adjustments if new keys are added to the index later on. It can be used in conjunction to # 1 to keep transparency about the alias.

I lean toward # 1. @thisismattmiller @tventimi would this affect your API clients significantly?

[tventimi]

I think #1 should be fairly easy to adapt to in the clients I am developing. Thank, @scossu .

[thisismattmiller]

Which ever you rather is fine with me.

If going with #1 it would require changes to the BF editor and LC FOLIO Toolkit, so whenever you have an example of what the /languages would return we can get started on updating our tools.