Server integration test for Device Flow (#3)

Extracted test cases from OAuth2Code flow tests to reuse in device flow

deviceHandler unit tests to test specific device endpoints

Include client secret as an optional parameter for standards compliance

Signed-off-by: justin-slowik <justin.slowik@thermofisher.com>

storage/sql/migrate.go

@@ -235,6 +235,7 @@ var migrations = []migration{
 				user_code text not null primary key,
 				device_code text not null,
 				client_id text not null,
+				client_secret text ,
 				scopes bytea not null, -- JSON array of strings
 				expiry timestamptz not null
 			);`,