Add email domain registration and verification endpoints

[tmthecoder]

Add email domain registration and verification endpoints

Context

We need to add an api-gateway endpoint for email domain registration and verification

Acceptance Criteria

Domain Registration:

• Will be used with sendgrid's registration service (https://docs.sendgrid.com/api-reference/domain-authentication/authenticate-a-domain)
  • We only need to get the domain, and subdomain parameters

Domain Verification:

• Will be used with sendgrid's domain validation (https://docs.sendgrid.com/api-reference/domain-authentication/validate-a-domain-authentication)
• Need to intake the domain. We will keep a mapping of domain to id in Juno-specific database

Both:

• Need an Authorization header containing a JWT which will be validated with the JWT middleware

Testing

• Please ensure there are tests written for the following cases (at a minimum):
  • Calling the registration endpoint with malformed domain/subdomain parameters
  • Calling the registration endpoint with missing domain/subdomain parameters
  • Calling the registration endpoint with correct domain/subdomain parameters
  • Calling the validation endpoint with malformed a domain parameter
  • Calling the registration endpoint with a missing domain parameter
  • Calling the registration endpoint with a correct domain parameter