Improve connection string parsing for TLS certificates

## What did you do?

When creating a new server from a postgres connection string, Postico does not seem to parse the `sslcert/sslkey/sslrootcert` query parameters properly, and does not fill the path for the `Server CA/Client Cert/Client Key` inputs.

My connection string looks like this:

```
postgres://username:password@127.0.0.1:15432/database?sslcert=/tmp/tmp.DSb7o56gRA&sslkey=/tmp/tmp.h2J1LhJtt4&sslrootcert=/tmp/tmp.IWNE6enikG
```

## What did you expect to happen?

I expected Postico to fill all the inputs from the parameters I specify in my connection string.

## What actually happened?

The paths are not parsed and the inputs are not filled.

## What software versions are you using?

Postico version: 2.0.5 (9661)

Start at the new-server flow that parses PostgreSQL connection strings, focusing on the sslcert, sslkey, and sslrootcert parameters. Verify that the Server CA, Client Cert, and Client Key inputs are populated from those paths, and confirm the example connection string works.

Written by the indexing model from the issue text.