CamelCase Defs

[mscuthbert]

(Initial discussion Superseded; see below the line for current discussion)

(from discussion #446)

In the JSON Schema, currently a reference in `$defs` for an object-type (Class) is only made on the second usage. I propose that the `$defs` reference be created on first usage. Why?

1. Every object-type currently has a name in the Django/sqllite database and this is referenced in the docs. However, these names are not exposed in the Schema except for objects with 2+ usages. This change would make either the schema or the Django reference a point of truth (p.s. -- I hope that eventually the schema can be considered the main point of truth).
2. In the Typing of objects #446 discussion, names for classes of objects are becoming important for many users -- putting the name of an object-class near the object-class definition seems very valuable.
3. According to "Understanding JSON Schema": "the $defs keyword gives us a standardized place to keep subschemas intended for reuse in the current schema document" -- because objects can be identified by id, etc. they should be considered intended for reuse even if we haven't yet used them twice in the document.

I wrote all this and now I see that this has been done with the vendors and _x work! WOW! Yes! I'll keep this for justification in case it's challenged.

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With this notion that object names might be used as class names, I also propose that hyphens be removed from $defs references -- at least for {} objects if not also things like positive-integer -- and that camelCase or ObjectCase be used instead. This will help find odd usages like the present "multimeasureRests": {"$ref": "#/$defs/multimeasure-rests"}

I also think it's probably helpful to change the current root to _root or _mnxroot so that the starting definition for the entire doctree is at the beginning rather than happening to be between rhythmic-position and score -- yes, we're not optimizing for human reading, but even today's AIs will prioritize things at the beginning. when summarizing, and I'm certainly not the last human to look at the schema.

[mscuthbert]

One other proposed change: move the schema out of /docs/ and into /specification/? I know that it's currently generated from the docgen system and sqllite source, but I always look for it in specification and am surprised to find it in docs.