Unreviewed tomograms should not have a quality score by default

[kandarpksk]

Based on a discussion of feedback form responses, when the quality of a tomogram is not reviewed, the quality score should appear as unrated (tentative language) rather than defaulting to any value (currently rating of 4 I believe).

Ask:

• support null values
• quality scores should not auto default to the value of 4 if not reviewed

[junxini]

@uermel i think the primary action is on the data updates for this. could you take a look when you're back?

[daniel-ji]

Update (via discussion with @uermel, @anchi2c, @manasaV3):

In addition to the current 1-5 values permitted for tiltseries quality, null is another value that should be accepted by the backend and displayed on the frontend as unrated (not set in stone, cc: @uermel @junxini).

See chanzuckerberg/cryoet-data-portal-backend#217 for the backend changes.

[daniel-ji]

Note this is currently blocked, waiting for alignment data to get surfaced so that null values have more context, see the backend PR (listed above)

[junxini]

note: push out until standard tomograms are done

[junxini]

@Janeece from a design perspective:

1. what's your recommendation on how null values should show up in the table view (example)?
2. how should the value show up in the filter dropdown on single dataset page?