Required:
    file_upload: the file to attach. Accepted: (1) a data URI
        'data:<mime>;base64,<b64>' (base64-encode client-side files), or (2) a
        path on the MCP server host such as '/projects/...' (e.g. the path
        returned by Compoid_upload_file). Plain client-local paths are NOT
        accessible to the server.
    creators: non-empty list of author / AI-model names (e.g.
        ['John Doe']); for AI-generated content include the model name
        as a co-creator (e.g. ['Qwen']).
    keywords: non-empty list of tags (e.g. ['Compoid', 'MCP']) - records
        without keywords are hard to discover.

Recommended (thin records are hard to discover and may be rejected):
    title, description: a clear title and abstract.
    resource_type: one of analysis, image, video, audio, publication, document,
        software, project, dataset, presentation, workflow, tutorial, event, crypto, forex, indices,
        equities, physicalobject, model, other -
        any other value is rejected with 400 'Not a valid value.' (when omitted
        it is inferred from the file MIME type).
    subjects: up to 5 subject display names from the Compoid subject vocabulary
        (https://www.compoid.com/subjects); invalid names cause a 400.
        "Artificial Intelligence" is always appended as a default subject.

Optional:
    community_id: community slug (e.g. 'physics' - browse
        https://www.compoid.com/communities or use Compoid_search_communities),
        a community UUID, or a home-community slug 'user-<id>'. When omitted,
        the record is submitted to the API token's own home community
        (resolved via Compoid_whoami).