Find or create assets tags on import, fixes #2439

[dancgray]

Apply tags from assets.json for each asset.

[canstudios-nicolaw]

I am getting error

ReferenceError: _ is not defined
    at /app/plugins/filestorage/localfs/index.js:235:17
    at /app/plugins/filestorage/localfs/index.js:464:12

When I try to import a course which contains a single asset with a tag.

Adding const _ = require('underscore'); to plugins/filestorage/localfs/index.js fixes this for me

After adding this line I have tested and this works well.

[tomgreenfield]

If it's just that file, might be worth changing the one Underscore reference to something in the current spec:

adapt_authoring/plugins/filestorage/localfs/index.js

Line 235 in 95f04bd

data = _.extend(data, withMeta);

i.e.

data = { ...data, ...withMeta };

or

data = Object.assign(data, fromMeta);

[Link2Twenty]

data = Object.assign(data, fromMeta);

Object.assign updates the first property so it can just be written

Object.assign(data, fromMeta);

[canstudios-nicolaw]

Works for me

[taylortom]

...with the comment fixed

[taylortom]

Do we need to return early if an error is returned by the cb? Assuming the next line would fail if the record isn't there.