enabler(backends): allow ssl string parameters in PostgreSQL URL (#575)

The underlying library asyncpg accepts string values in the ssl
parameter. The old code only accepted the values true and false, which
are converted to boolean.

databases/backends/postgres.py

@@ -55,7 +55,8 @@ def _get_connection_kwargs(self) -> dict:
         if max_size is not None:
             kwargs["max_size"] = int(max_size)
         if ssl is not None:
-            kwargs["ssl"] = {"true": True, "false": False}[ssl.lower()]
+            ssl = ssl.lower()
+            kwargs["ssl"] = {"true": True, "false": False}.get(ssl, ssl)
 
         kwargs.update(self._options)
 

tests/test_connection_options.py

@@ -46,12 +46,24 @@ def test_postgres_ssl():
     assert kwargs == {"ssl": True}
 
 
+def test_postgres_ssl_verify_full():
+    backend = PostgresBackend("postgres://localhost/database?ssl=verify-full")
+    kwargs = backend._get_connection_kwargs()
+    assert kwargs == {"ssl": "verify-full"}
+
+
 def test_postgres_explicit_ssl():
     backend = PostgresBackend("postgres://localhost/database", ssl=True)
     kwargs = backend._get_connection_kwargs()
     assert kwargs == {"ssl": True}
 
 
+def test_postgres_explicit_ssl_verify_full():
+    backend = PostgresBackend("postgres://localhost/database", ssl="verify-full")
+    kwargs = backend._get_connection_kwargs()
+    assert kwargs == {"ssl": "verify-full"}
+
+
 def test_postgres_no_extra_options():
     backend = PostgresBackend("postgres://localhost/database")
     kwargs = backend._get_connection_kwargs()