Add flag file for state "Waiting for Server"

[AlbertoCasasOrtiz]

Tasks (Frontend and Backend):

• [ ] Create flag file (called waitingForServerFlag or something similar) when user click "Process" or "Reprocess".
• [ ] Remove flag file when the task is queued in slurm.
• [ ] Remove an old file and create a new one when "Process" or "Reprocess" is clicked (so it updated the creation date).

Tasks (Frontend):

• [ ] Check for presence of the waitingForServerFlag.

• [ ] If it exists and has been created more than 24 hours ago, ask user to reprocess.

  Note: Looks like flag files are created and removed in frontend or backend as needed?

[AlbertoCasasOrtiz]

@nickbianco I noticed that a flag for "Waiting for Server" is equivalent to:

readyFlagExists && !resultsExist && !errorFlagExists && !processingFlagExists && !slurmFlagExists

So I am using this expression for now. We could create a variable in the frontend for it without specifically having to create a flag and pollute the file system with more files.

[nickbianco]

@AlbertoCasasOrtiz sounds good!