Feat: Store content type parameters

[Falx]

📁 Related issues

#458

✍️ Description

Initial plan, but will not implement now
Replacing the RepresentationMetadata#contentType currently in use (as a string) with an object that also contains the parsed parameters would lead to a lot of changes in the codebase (and in testing). The main issue being that the RepresentationMetadata class would no longer consist of only single <identifier> <predicate> <object> triples to store metadata. The new contentType would need something along the lines of this structure:

<> ma:format _:format.
_:format     solid-type:value     "application/json";
             solid-type:parameter _:parameter1.
_:parameter1 rdfs:label           "charset";
             solid-type:value     "utf-8".

All internal code that now works on the assumption that they can just set a metadata property with one predicate and one value breaks now. The same thing is true for code that removes this triple/quad by identifying it as the triple using the <ma:format> predicate.

Proposed solution
After some internal discussion with @joachimvh, we've decided on the following strategy for now:

• Leave the current contentType syntactic sugar on the RepresentationMetadata class for now so that we don't break any existing code in the CSS.
• Add a syntactic sugar for contentTypeObject to retrieve a new ContentType object with the following structure:

  {
     "value": "text/plain",
     "parameters" : {
         "chartset": "utf-8"
     }
  }

• On setting the contentType, the optional parameter string is also parsed and stored in the RepresentationMetadata like this:

  <>       solid-meta:ContentTypeParameter _:param1.
  _:param1 rdfs:label                      "charset";
           solid-type:value                "utf-8".

This allows developers who want, to also request the complete ContentType object using metadata.contentTypeObject and use the parsed parameters. When assigning a new value to metadata.contentType, the parameters will first be cleared from the metadata. To explicitly remove all parameters and contentType: metadat.contentType = undefined does this for you.

I've added extra tests to test the behaviour described above.

✅ PR check list

Before this pull request can be merged, a core maintainer will check whether

• this PR is labeled with the correct semver label
  • semver.patch: Backwards compatible bug fixes.
  • semver.minor: Backwards compatible feature additions.
  • semver.major: Breaking changes. This includes changing interfaces or configuration behaviour.
• the correct branch is targeted. Patch updates can target main, other changes should target the latest versions/* branch.
• the RELEASE_NOTES.md document in case of relevant feature or config changes.

[joachimvh]

I agree with the general idea, there are just some code changes that can simplify everything I think. Also the classes that currently parse the content-type should be updated (mentioned in one of the comments below).

[Falx]

I've incorporated all changes discussed before.

[joachimvh]

Mostly just some minor nitpicks. Some commits from the main branch also snuck in here.

[joachimvh]

Looks good, thanks!