Modify audio columns

[krysal]

In line with WordPress/openverse-api#141, this PR:

• Add watermarked column to the schema of the audio table in SQL files
• Rename the genre column to genres and changes its type to a Postgres array field
• Rename the alt_audio_files column to alt_files
• Keep the old standardized_popularity column for image and audio tables.

[dhruvkb]

view_count is also a non-nullable field in media. The sample data for images (in openverse-api) contains a view_count column with all values set to zero, can this be reproduced for audio?

[dhruvkb]

This should be a string array column. In PostgreSQL they are represented by varchar(<len>)[] and the data can be stringified as {<item 1>,<item 2>...}.

The current implementation of genres is varchar(80)[].

[krysal]

Working on this, it's needed to add the new column type.

[krysal]

I'm not sure how view_count will fit within the audio table, is not in the schema of the image table, only in the old one and apparently it's not used.

[dhruvkb]

If it's no longer used, should/can we remove it from the API models and sample data as well?

I think it's best to remove fields that are no longer used, but we should loop in @obulat and @zackkrida for their opinions on this.

[zackkrida]

I agree that we should remove view_count, it can be safely removed from everywhere it appears.

[krysal]

This is ready for review, can be tested with an audio API provider script, like Jamendo, and should load the audio table with the columns changed.

For example, the genres column as an array of character varying(80):

[dhruvkb]

LGTM 👍 (We can remove the view_counts in a separate PR later on)