New metadata for comics and periodicals

[HadrienGardeur]

This is still a draft PR but its focus is on belongsTo and a new contains metadata.

This work is based on https://gist.github.com/HadrienGardeur/212d66372ea7433f59591afae2c3a605

For now I've focused strictly on the JSON Schema, I plan on drafting more spec language once we've reached an agreement on the schema first.

A publication can now belong to one or more:

• collection
• journal
• magazine
• newspaper
• season
• series
• story arc
• volume

A publication can now contain one or more:

• article
• chapter
• episode
• issue
• season
• series
• story arc
• volume

A series can now contain one or more:

• chapter
• episode
• issue
• season
• story arc
• volume

A season can contain one or more:

• episode

A volume can contain one or more:

• chapter
• issue

A story arc can contain one or more:

• chapter
• episode
• issue

An issue can contain one or more:

• article
• chapter

A periodical (journal, magazine or newspaper) can contain one or more:

• issue
• volume

An article behaves a bit more like a publication and can be described by:

• a name
• an identifier
• a description
• one or more author
• one or more translator
• one or more editor
• one or more artist
• one or more illustrator
• one or more contributor
• a number of pages

All of these structures can contain links.

[HadrienGardeur]

I'll do a second pass at this once I'm done inspecting the following schemes:

• https://anansi-project.github.io/fr/docs/comicinfo/documentation
• https://metron-project.github.io/docs/metroninfo/schemas/v1.0

One thing that I can already say: I'm not too interested in expressing the total number of chapters/episodes/issues/seasons/volumes. But this can easily be addressed using the built-in extensibility for schema.org: https://schema.org/numberOfItems

[HadrienGardeur]

Also tagging people that have interacted with RWPM/OPDS 2.0 for comics before: @gotson @majora2007 @ajslater @chocolatkey @fillito

We previously discussed some of this in #96

With support for links in all of these properties, it should provide a very robust way of expressing this information AND explore it in a catalog.

[HadrienGardeur]

I'll do a second pass at this once I'm done inspecting the following schemes:

• https://anansi-project.github.io/fr/docs/comicinfo/documentation
• https://metron-project.github.io/docs/metroninfo/schemas/v1.0

Based on this review, I've added the concept of storyArc as well.

The other relevant bits are related to covers with cover artists and alternate covers, but that's for a separate PR.

[HadrienGardeur]

This PR has been opened for a while now but we haven't received much feedback, aside from a minor review comment from @chocolatkey.

Without additional feedback, I'll most likely merge it in early December. I know that @JamesEnglish1028 has been waiting for this, so I don't want to delay things for much longer.

Tagging a number of people once again: @gotson @majora2007 @ajslater @fillito