Replace the randomized secret key with a static key

Replace the randomized secret key with a static key to prevent errors with multiple instances running on App Engine. On other environments, a random key is generated. The CI/CD pipeline automatically includes the secret key from a file when deploying.

.gitignore

@@ -139,4 +139,6 @@ cython_debug/
 
 package-lock.json
 
-TODO.txt
\ No newline at end of file
+TODO.txt
+
+config/
\ No newline at end of file