✨ Added more robust database configuration to solution server

[JonahSussman]

Added better handling of the generation of the db_dsn field in SolutionServerSettings.

New environment variables added:

• KAI_DB_DRIVERNAME
• KAI_DB_USERNAME
• KAI_DB_PASSWORD
• KAI_DB_HOST
• KAI_DB_PORT
• KAI_DB_DATABASE

It now goes through the following flow:

1. Any parameters supplied via Python's SolutionServerSettings constructor takes highest precedence, then any configuration supplied via KAI_DB_DSN.
2. Try to parse KAI_DB_DSN as a json object, containing drivername, username, etc... If that fails, parse it as a connection string.
3. If the KAI_DB_DSN environment variable or the db_dsn field is not supplied, try to get all information from the new variables

[fabianvf]

LGTM