Decouple image (URI) shape matching from specific image file types/extensions

The intent has been from the start to avoid adding "Drupalism" to SDC's use of JSON Schema.

That's why we started using /schema.json and defined $ref: json-schema-definitions://experience_builder.module/image-uri.

However, given that ✨ [PP-1] Make link widget autocomplete work (for uri and uri-reference props) Postponed is proposing to add a variation for format: uri named format: uri+entity_autocomplete (which required a core change: 🐛 ComponentValidator ignores the set validator and creates a new one Active ) 

So, an alternative HERE could be that we start using custom formats (for type: string). Which is exactly what @lauriii expressed he'd strongly prefer over at #3462705-47: [META] Missing features in SDC needed for XB → . (Note that JSON Schema does support custom format attributes: https://json-schema.org/draft/2020-12/json-schema-validation#section-7 + https://json-schema.org/draft/2020-12/json-schema-validation#name-custom...)

Or better yet: use contentMediaType.

So then we'd go from:

    "image-uri": {
      "title": "Image URL",
      "type": "string",
      "format": "uri-reference",
      "pattern": "^(/|https?://)?.*\\.(png|gif|jpg|jpeg|webp)(\\?.*)?(#.*)?$"
    },

to:

    "image-uri": {
      "title": "Image URL",
      "type": "string",
      "format": "uri-reference",
      "contentMediaType": "image/*"
    },

… which is not quite exactly how contentMediaType is meant to be used (that's really describing the contents of the string itself), but is … close enough? Something along these lines has been proposed as resourceMediaType.

Examples of actually defining new JSON Schema formats seem impossible to find.

This would then also allow us to apply a similar improvement to "video URLs", which is being added at ✨ Define JSON Schema $refs for linking/embedding videos and linking documents Active .

Related but different: 📌 Decouple image shape matching from the `image` MediaType Active .