feat: new behaviour and multiple emails support (APP-145, APP-146)

[astansler]

• POST user now used for sending new user emails
• GET user now used for receiving for known emails (unverified emails not sent now, TODO)
• POST repo used now called once per repo at the begging of hashing and used to upsert repo and get presented commit history for repo
• POST complete used for notification of server that hashing of all repos completed (not per per repo as before)
• POST authors used for saving of all emails from repo and making association for useremail and repo for existing and new emails

P.S. Additional email commands not yet implemented

[yandzee]

Looks clear.