Add command for asset metadata re-extraction

[jjnesbitt]

Closes #1450
Closes #1118

[yarikoptic]

What's your plan @AlmightyYakob here - wasn't it close to completion?

[jjnesbitt]

What's your plan @AlmightyYakob here - wasn't it close to completion?

I unfortunately fell behind on this, as other things took priority. There are still logistical issues to work out on this PR, and at the moment my current priority is the embargo re-design. After that, I could take another pass at this.

[yarikoptic]

this might be relevant in the scope/to address

• assetMetadata not up-to-date or 000020 #1970

my current priority is the embargo re-design. After that, I could take another pass at this.

embargo is a curse! ;) we should see how to move this from the stalled point. attn @waxlamp

[yarikoptic]

in principle even

• Do re-validate dandisets upon dandischema upgrade #2024

is related here since we might want to redo extraction upon dandischema upgrade.

@jjnesbitt do you have plans to get back to this PR?

[jjnesbitt]

I believe this is ready to go. @jwodder or @yarikoptic can you verify that the nwb2asset function is being used correctly? As far as I'm aware from local testing it seems to be working correctly, but I don't exactly have a very good example asset to test the before and after. If you have a good example asset for this, that would also be helpful.