Support generic PostgreSQL DB args to allow for ssl-mode settings

[darthhexx]

Adds support for generic connection string arguments for PostgreSQL so that SSL mode and TLS certificates can be configured.

For example:

POSTGRES_DATABASE_ARGS="sslmode=verify-ca&sslrootcert=/app/certs/server-ca.pem&sslcert=/app/certs/client-cert.pem&sslkey=/app/certs/client-key.pem"

[Copilot]

Pull request overview

This PR adds support for configuring generic PostgreSQL connection string arguments via the POSTGRES_DATABASE_ARGS environment variable, enabling SSL mode and TLS certificate configuration for PostgreSQL connections.

Key Changes:

• Introduces POSTGRES_DATABASE_ARGS environment variable to accept custom connection parameters
• Appends these arguments as query parameters to the PostgreSQL connection string for TCP connections

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[Copilot]

The POSTGRES_DATABASE_ARGS are not being URL-encoded before appending to the connection string, while other parts of the connection string (username, password, database name, host) are properly encoded using urllib.parse.quote_plus(). This inconsistency could lead to connection string parsing issues if the args contain special characters. The args should be properly encoded or validated to ensure they're already in the correct format for URL query parameters.

Suggested change

	connection_suffix = f"{connection_suffix}?{POSTGRES_DATABASE_ARGS}"
	# Properly encode the query parameters
	args_pairs = urllib.parse.parse_qsl(POSTGRES_DATABASE_ARGS, keep_blank_values=True)
	encoded_args = urllib.parse.urlencode(args_pairs, quote_via=urllib.parse.quote_plus)
	connection_suffix = f"{connection_suffix}?{encoded_args}"

[Copilot]

The POSTGRES_DATABASE_ARGS are only appended when POSTGRES_USE_UNIX_SOCKET is False (TCP connections), but not when it's True (Unix socket connections). The Unix socket connection string on line 78 already includes query parameters (the host parameter), so additional database args should be supported there as well using an ampersand (&) to append them. This creates an inconsistency where SSL settings and other connection arguments cannot be used with Unix socket connections.

Suggested change

	else:
	connection_suffix = f"{urllib.parse.quote_plus(POSTGRES_USER)}:{urllib.parse.quote_plus(POSTGRES_PASSWORD)}@{DB_HOST}:{DB_PORT}/{urllib.parse.quote_plus(POSTGRES_DB)}"
	if POSTGRES_DATABASE_ARGS:
	connection_suffix = f"{connection_suffix}?{POSTGRES_DATABASE_ARGS}"
	if POSTGRES_DATABASE_ARGS:
	connection_suffix = f"{connection_suffix}&{POSTGRES_DATABASE_ARGS}"
	else:
	connection_suffix = f"{urllib.parse.quote_plus(POSTGRES_USER)}:{urllib.parse.quote_plus(POSTGRES_PASSWORD)}@{DB_HOST}:{DB_PORT}/{urllib.parse.quote_plus(POSTGRES_DB)}"
	if POSTGRES_DATABASE_ARGS:
	connection_suffix = f"{connection_suffix}?{POSTGRES_DATABASE_ARGS}"

[Copilot]

The new POSTGRES_DATABASE_ARGS functionality lacks test coverage. Since tests/test_config.py already validates other configuration values, consider adding tests that verify the connection string is constructed correctly when POSTGRES_DATABASE_ARGS is set, including scenarios with special characters, multiple parameters, and both TCP and Unix socket configurations.