Goal: 

• Add API and database support for listing/searching environments of repositories.
• Support should have already been added in yummy.

Acceptance Criteria:

• Add `repositories/{uuid]/environments/` endpoint for listing
• Add `environments/names/` endpoint for searching. 
• Functionality should be just like RPMs search and list endpoints. 
• Search API should de-duplicate environments for a given name, e.g. the same environments can exists across repos 
• Should return ID, Name, and Description metadata.
• Add database support to store environment metadata.
• Environments should be de-duplicated based on combination of name/ID