Add RDAP data endpoint in manage.get.gov API

Issue description

To enable users to view domain registration information, we are using WHOIS/RDAP to look up the registration data of a domain. However, GFE devices are blocked from accessing WHOIS due to being equipped with ZScaler, which blocks WHOIS. This prevents users on GFEs from accessing WHOIS data.

Because manage.get.gov is serviced through cloud.gov, we will be adding a public API endpoint that acts as middleware to fetch WHOIS/RDAP data. The API endpoint can then be called on other .gov services without being blocked by ZScaler.

Acceptance criteria

[x] Create a public RDAP API endpoint in the registrar that takes in a domain name and returns a JSON of its RDAP data
[x] Append .gov if there is no TLD associated (going to interpret this as the input having no .) similar to how availability API appends .gov to inputs without TLD - [ ] the api should provide an error in the json response if the domain ends in something other than .gov; however, it should except a domain with no suffix and it should append a .gov in this case (just like the availability api) ~~- [ ] the api provide an error in the json response if the domain is not found~~
[x] Add necessary tests for API endpoint functionality ~~make new class to mock basic RDAP responses~~
[x] the api should be modeled much like the api for availability. suggest also utilizing caching on the api endpoint such as with @ttl_cache(ttl=600) // Add a comment in ttl_cache that this may affect memory since it's storing this info in the system memory to keep in mind for memory issues down the road and we need to reevaluate cache time

Additional context

Removed ACs above because RDAP returns JSON with error handling which is then parsed on get.gov's end

No response

Links to other issues

blocks: #316

@abroddrick re: the 2nd AC that got added - the RDAP API already returns JSON indicating a bad request was made when you query an invalid .gov domain (either because it doesn't end in .gov or it does not exist as a .gov domain). Given RDAP's APIs has different conventions from the EPP API, do we want to have different error handling for the two as well?

RDAP gives more robust error descriptions when you give it an invalid domain to query but I can also be convinced we should handle these errors on our own API's end to minimize calls to RDAP

// Example of inputting whitehouse into RDAP

...
 "description": [
    "whitehouse is not a valid domain name: Domain name must have exactly one part above the TLD"
  ],
  "errorCode": 400,
  "title": "Bad Request",
...

// Example of inputting whitehouse.com into RDAP

...
 "lang": "en",
  "description": [
    "whitehouse.com is not a valid domain name: Domain name is under tld com which doesn't exist"
  ],
  "errorCode": 400,
  "title": "Bad Request",
...

cisagov / manage.get.gov