Improve the OPDS category API

[kelson42]

We have a list of categories currently available at https://library.kiwix.org/catalog/v2/categories.

IMO, this is a "good start" but its missing a few things:

• We should have a label
• The label should be somehow localised
• We should deliver a URL to have a picture for the category

Then I have other points which are less clear to me:

• We propose a link with a subsection, I wonder if the category "Other" shoudl not provide a link delivering anything which is not in the other categories
• I wonder if the description of the filter given is really necessary
• If we keep the description of the filter, then we should probably consider to provide translated version as well

This ticket is not a request to implement all the points above, but to discuss them so we can go forward later, on the consensual ones.

[rgaudin]

I think we should prioritize the features we need to replicate current reader usage an add the additional ones later on.

• We should have a label
• The label should be somehow localised

Only other and mooc would benefit from it as others are brand names. I understand that may be useful but storing this information is gonna be an issue.

• We should deliver a URL to have a picture for the category

Important as it's already in use in Kiwix iOS. What they do is they use the first ZIM's Icon from that category as category icon. Not flexible but it has the advantage of solving the storage question and the format/dimension one.

Using this to remind that we still only provide and support 48px as illustration which is small and can only be used as a tiny icon. Probably the reason why kiwix iOS doesn't display it except inline in the ZIM list.

Then I have other points which are less clear to me:

• We propose a link with a subsection, I wonder if the category "Other" shoudl not provide a link delivering anything which is not in the other categories

Definitely. As a user, I would expect any categorization system to not give access to all the catalog. So either we use other or we add a special uncategorized filter but we need to access the whole catalog using this concept.

• I wonder is the description of the filter given is really necessary
• If we keep the description of the filter, then we should probably consider to provide translated version as well

Part of the spec I think. Could be rewritten and yes, translated but unless we have meaningful insight provided here that the readers would reuse directly, it's probably not worth the trouble. Where would that be stored?