-- Metadata of jobs to be fetched by the scheduler and to be
-- assigned to the workers
-- part of the *new* job system
JobMeta
  occurrence           JobOccurrence      -- When should the job be executed?
                                          -- (Possibly recurring)
  relativeInTime       TimeRelative Maybe -- TODO find better name
  planExecutionAhead   NominalDiffTime    -- TODO find better name
  executionTimeEpsilon NominalDiffTime Maybe
  priority        JobPriority
  ressources      JobRessources
  status          JobStatus
  lastStartSystem UTCTime Maybe -- when did a job scheduler last order 
                                -- a job worker to execute this job?
                                -- when a job is to be executed now, 
                                -- lastStartWorker and lastFinished 
                                -- are unset
  lastStartWorker UTCTime Maybe -- when did a job worker last start 
                                -- executing this job?
                                -- when no time is set, the job either 
                                -- was never executed yet or execution 
                                -- was just ordered (or something went 
                                -- very wrong within the jobsystem)
  lastFinished    UTCTime Maybe -- when did a job worker last report 
                                -- successful execution?
  -- all "last..." fields should be set by the scheduler atomically!
  retryAfter NominalDiffTime Maybe -- if set, the scheduler checks on 
                                   -- the job after this time and retries 
                                   -- the job iff lastStartWorker is set, 
                                   -- but lastFinished is unset
                                   -- Ensure that retryAfter is sufficient 
                                   -- for this job and application, so better 
                                   -- set to higher values until we know this 
                                   -- job is definitely dead after execution
                                   -- (pun intended)
  isSystemJob Bool -- new system jobs are to be scheduled, old system jobs to be deleted on migration
  appVersion AppVersion
  deriving Eq Ord Show Generic

-- Actual job to be fetched and executed by the workers
-- part of the *new* job system
JobData
  meta       JobMetaId
  content    Value  -- JSON representation of the job content
                    -- (parsing as generic Aeson Value 
                    --  instead of Job for compatibility with 
                    --  legacy jobs)
  deriving Eq Ord Show Generic