cove_bods/process.py: Fix ConvertJSONIntoSpreadsheets error handling

[radix0000]

Create temporary file if flattentool fails and use to propagate error to user

#100

[odscjames]

One change - currently the path is being made with

 filename = f"{name}-{id}-error.json"

It should really be made inside the directory with the other files for this bit of supplied data - see how paths are made like:

os.path.join(self.supplied_data.storage_dir(), "the-filename"),

(self here is the process task class)

This is because when we expire data, we delete all the actual data and results from the file system (we just keep some meta-data in the database so we can track usage). We do this by just deleting that directory and all it's contents, so all files should be inside the directory so they get deleted too. https://github.com/OpenDataServices/lib-cove-web-2/blob/main/libcoveweb2/management/commands/expire_files.py

[radix0000]

Have moved creation of temporary file into self.supplied_data.storage_dir()