Jamesdemery/bb2 4190 ensure consistent 404 responses

[JamesDemeryNava]

JIRA Ticket:
BB2-4190

What Does This PR Do?

Ensures consistent 404 responses for when a user runs a patientV2 call for a fhir_id they are not associated with or for a fhir_id that does not exist. Previously, two different error messages were reported.

What Should Reviewers Watch For?

If you're reviewing this PR, please check for these things in particular:

Validation

Ensure the new unit tests, test_read_on_different_fhir_id_than_associated_with_token and test_read_on_fhir_id_that_does_not_exist cover the cases that we want.

Open Postman, run the following cases and confirm both return a 404 with detail = 'Not found.':

1. Use a different fhir_id than the one you have a token for, but one that does exist in your local DB. Run the patientV2 API call and confirm that you get a 404 with detail of Not found.
2. Use a fhir_id that does not exist in your local DB (or anywhere - usually start the fhir_id with -99 to make sure it DNE anywhere), run the patientV2 API call and confirm you get a 404 with detail of Not found.

What Security Implications Does This PR Have?

Please indicate if this PR does any of the following:

• Adds any new software dependencies
• Modifies any security controls
• Adds new transmission or storage of data
• Any other changes that could possibly affect security?

• Yes, one or more of the above security implications apply. This PR must not be merged without the ISSO or team
  security engineer's approval.

Any Migrations?

• Yes, there are migrations
  • The migrations should be run PRIOR to the code being deployed
  • The migrations should be run AFTER the code is deployed
  • There is a more complicated migration plan (downtime,
    etc)
• No migrations