Add species stats schema and a mapping between fields in response and attribute names in db

Created by: azangru

Description

• Added an open API spec for Species Stats schema (converted automatically from a typescript file)
• Added a json file containing a mapping between fields in the proposed Species Stats schema and the names of the attributes in the metadata database

Note

• Didn't know where to put the files. Couldn't find any dedicated place for them; so put them in the root.
• The open api spec file in the PR focuses on the schema. It does not prescribe what to do when the client sends a request with a wrong http verb, etc. Please use your own judgement to handle this as json apis normally do
  • Having said that, one special case that web client is interested in is that in case the genome with a given genome id is not found, the server respond with a 404 status.

Related Jira tickets

• https://www.ebi.ac.uk/panda/jira/browse/EWB-434
• https://www.ebi.ac.uk/panda/jira/browse/EWB-515