Read the FileStack Key from environment variable for both dev and prod deployment

[LieutenantRoger]

Currently the codebase are having a default value for FILESTACK_API_KEY and FILESTACK_SUBMISSION_CONTAINER key variables,

We need to remove the default keys in the codebase and read the values from the environment for both dev deployment and prod deployment.

[LieutenantRoger]

This is fixed