Arvados

Generalize the special case in jobs.create.

Add optional find_or_create flag to create method. If set:

• If filters parameter is provided, look up objects using those filters.
  • If exactly one result is found, return that.
  • If no results are found, create a new object as usual.
  • If >1 results are found, return an error.
• If filters parameter is not provided, look up objects using the provided resource_attrs as a where parameter, and proceed as above.

Jobs.create should be rearranged to use the generic mechanism.

• Move no_reuse (and other params that aren't actually resource attributes) out of resource_attrs, e.g., params[:job][:minimum_script_version]=X should move to something like params[:filters]=[['script_version','>=',X]] and JobsController should override apply_where_limit_order_params to use find_commit_range when >= and <= filters are used with the script_version attribute.
• Implement exclude_script_versions=X as params[:filters]=[['script_version','not in',X]] (adding a "not in" operator should be trivial)
• Implement the range logic so the client can do commit range lookups itself using list, not just implicitly via create