[REFACTOR] Configure Secret or Env instead of hardcoded key

src/main/resources/application.properties

 spring.application.name=authentication
 spring.profiles.active=${PRODUCTION:dev}
 google.client.id=${GOOGLE_CLIENT_ID:default}
-google.client.secret=${GOOGLE_CLIENT_SECRET:default}
\ No newline at end of file
+google.client.secret=${GOOGLE_CLIENT_SECRET:default}
+jwt.secret=${JWT_SECRET:biggerboysandstolensweetheartsss}
\ No newline at end of file