Enable running postgres on a port that isn't 5432

[mattdailis]

Checked for duplicates

No - I haven't checked

Alternatives considered

No - I haven't considered

Related problems

Port 5432 is hard-coded in a number of places in the Aerie codebase. This makes it difficult to deploy Aerie on the same machine that's running another instance of postgres.

Describe the feature request

The database port environment variable should be used consistently across all services.

[Mythicaeda]

It is also hard-coded in the migration script.