This was a bit tricky and I ended up breaking things down a lot and
trying different path. This commit is the result of the most
satisfying one.
It introduces a new 'concept' and types: Definitions and Reference.
These elements are meant to reflect JSON pointers and JSON-schema
definitions which we now use for pretty much all user-defined
data-types.
In fact, Schemas are no longer inlined, but are always referencing
some schema under "definitions".
This indirection is necessary in order to cope with recursive types.
And while it's only truly necessary for recursive types, using it
consistently makes it both easier to produce and easier to consume.
---
The blueprint generation for recursive types here also works thanks to
the 'Definitions' data-structure wrapper around a BTreeMap. This uses
a strategy where:
(1) schemas are only generated if they haven't been seen before
(2) schemas are marked as seen BEFORE actually being generated (to
effectively stop a recursive generation).
This relies on one important aspect: the key must be uniquely
identifying a given schema. Which means that we have to monomorphize
data-types with generic parameters also here, and use keys that are
specialized in one data-type.
---
In this large overhaul we've also lost one thing which I didn't bother
re-introducing yet to keep the work manageable: title for record
fields. Before, we use to pull those from record constructor when
available, yet now, every record constructor has been replaced by a
`$ref`. We could theoritically attach a title to the reference. I'll
try to quickly add that in a later commit.
Having the data's schema be optional at the level of the 'Schema' did not allow to represent cases where there would be an opaque data at an arbitrary nesting. So I introduced a new variant 'Opaque' on 'Data' to fill that gap.
These functions relied on the same dependency and had the same scope. So insertion was by encounter rather than order determined by dependency handling. Now we switched to dependency order is prioritized to prevent free unique.
-Builitins IR now acts like Record IR in terms of argument consumption
-UnConstrData returns as Pair(Data,Data) to conform with how pairs are treated behind the scenes.
