Provide specific errors for database connection failures from the webserver

[ThomasLaPiana]

Is your feature request related to a specific problem?

If the webserver fails to connect to the database, a generic "database unreachable" error is given

Describe the solution you'd like

We should let the user know exactly which part of their configuration is incorrect (i.e. user/password, vs. completely unreachable)

Describe alternatives you've considered, if any

A description of any alternative solutions or features you've considered.

Additional context

should be done after #562

[allisonking]

After #649, the errors sqlalchemy raises by default seem pretty decent, for example:

• Wrong username/password for the db

Unable to reach the database: sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) FATAL:  password authentication failed for user "postgressss"

• Wrong port

fides-fidesctl-1  | 2022-05-17 20:37:37.249 [ERROR] (database:get_db_health:135): Unable to reach the database: sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) could not connect to server: Connection refused
fides-fidesctl-1  | 	Is the server running on host "fidesctl-db" (172.23.0.2) and accepting
fides-fidesctl-1  | 	TCP/IP connections on port 5431?
fides-fidesctl-1  | 
fides-fidesctl-1  | (Background on this error at: https://sqlalche.me/e/14/e3q8)

• Can't reach db host

fides-fidesctl-1  | 2022-05-17 17:27:55.022 [ERROR] (main:configure_db:53): Unable to configure database: sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) could not translate host name "fidesctl-db" to address: Name or service not known
fides-fidesctl-1  | 
fides-fidesctl-1  | (Background on this error at: http://sqlalche.me/e/14/e3q8)

Do you think that's enough, or is there more work to do for this ticket?

[ThomasLaPiana]

those 3 seem great! we want to make sure that its enough info for an end-user to reasonably debug any connection issue, and these three feel like they'd cover the vast majority of those issues

[allisonking]

Closed as a side effect of #649