Add email service RPC for sendgrid sender registration

[tmthecoder]

Add email service RPC for sendgrid sender registration

Context

We need to add an RPC endpoint to interface with Sendgrid's sender email registration API

Acceptance Criteria

• A Proto RPC with appropriate Request/Response types is generated for this RPC
• The Email Service implements the above RPC
  • This implementation should intake the parameters needed for Sendgrid sender registration (https://docs.sendgrid.com/api-reference/sender-verification/create-verified-sender-request)
  • We need to take in the from_email, from_name and reply_to parameters
  • Return the status code from sendgrid as well as the appropriate response message

Testing

• Please ensure there are tests written for the following cases (at a minimum):
  • Calling the rpc with a successful registration
  • Calling the roc with an unsuccessful registration