added last_modified timestamp to hidden inputs

[Manoj-nathwani]

Note: This is only fixing the single file uploader

Problem

• When uploading or editing url/file uploads we are never setting or updating the last_modified field on the resource

Solution

• Whenever updating the HiddenFormInputs field, update the last_modified with a ISO timestamp

Important gotchas

• The field may be slightly out-of-date as we only update the last_modified field whenever there is interaction with this react component. So if a user opens the page, waits 10mins before editing the description of the resource, then the timestamp on save would be 10mins old.
• The last_modified field is always updated, which means if a user edits a resource and makes no changes and hits save, then the last_modified would be the only field updated. If we want to ignore resource edits where the only change was the last_modified then we would need to add validation to the backend.

[tomeksabala]

1. (!!!) Last modified date is still not set with bulk upload
2. The last modified date must be only set if resource file is changed. Changing just the metadata should not update it. There's metadata_modified field for that.
3. We could decide that the last_modified date is equal to file successfully uploaded to giftless. You can't get the date from the form page load.

The last_modified field is always updated, which means if a user edits a resource and makes no changes and hits save, then the last_modified would be the only field updated. If we want to ignore resource edits where the only change was the last_modified then we would need to add validation to the backend.

That's buggy behavior as well but I believe it'll resolve itself after you fix 2 & 3.

[tomeksabala]

I think that the fact you need to remove tz info from the date string is a bug in ckanext-scheming.
Let's leave it for now (as it doesn't work otherwise) but I'll try to submit an issue.

[tomeksabala]

ckan/ckanext-scheming#291

[Manoj-nathwani]

Decided to move this into backend before_create and before_update so it's less hacky to support on the frontend