Allow importing from a series

[irrationalpie7]

Allow users to import from a series URL, importing tags (in the various categories such as fandom, relationship, etc) from all the works in that series.

Some things to consider:

• Some metadata (e.g. language and rating) are only allowed to have one value, but within a series might have multiple values. For rating, AO3 picks and shows the max (not sure how unrated works influence this). I'm not sure what to do about language--I guess we could just leave it blank if not everything in the series is the same, and then ao3 would complain when the user tried to save the work if they didn't pick anything themselves
• Pulling this info from each individual work in the series by going to its work page (which we already know how to parse) would quickly run into AO3's rate-limiting, so we should not do that
• The dom on a series page does seem to mark up the different kinds of tags with what category they belong to (e.g. character, freeform)
• Some info is only available on the works page, as far as I know (e.g., AO3 shows at most one "category" tag per work on a series page--F/F, M/M, Gen, Multi, etc)
• There's limits to the number of tags per work, that do not apply to tags for a series as a whole. If you go over the limit when trying to post a new work, AO3 won't let you save your draft until you're back under the limit. If there's a lot of tags, it could be very annoying to the user to manually get rid of the extras. Possibly we could show users an extra warning if they're going over the limit and tell them by how much?
• AO3 (a) doesn't allow you to set a series as the work that inspired you and (b) only lets you add one inspirational work per time you submit the new work form. I suggest listing the first work in the series as an inspiration and calling it a day

[jermowery]

For the initial release of this we can make it easier and accomplish most of what we want be leaving the ambiguous pieces blank. That would be:

• When language has multiple values do nothing
• When rating has multiple values do nothing
• When we go over the tag limit just go over the limit with no additional warning

Doing this will allow us to allow importing from a series, it wont be perfect but it will save people more time in the short term. We can then file a separate issue to address improving the other pieces here

[jermowery]

An example of a series: https://archiveofourown.org/series/2508355