docs(shacl): document rule-to-SHACL-SPARQL constraint generation - #3991

The rules-to-SHACL-SPARQL converter recognised two named patterns.  This
adds the presence-implies-value pattern: a precondition asserting
`value_presence: PRESENT` on one slot, and a postcondition constraining
another slot with `equals_string` or `equals_string_in`.  It reads as
"if the guard slot is present, the target slot must be present and hold
one of the allowed values", and generalises the boolean guard to
arbitrary enum values.  The boolean guard becomes the case
`equals_string: "true"` of this pattern on an xsd:boolean-typed flag.

`equals_string` / `equals_string_in` compare strings.  The metamodel
defines them for slots of range string; enums and types with datatype
xsd:string are treated alike, and a slot without a range takes the
schema's default_range.  On an xsd:boolean-typed slot each value must be
a lexical form of xsd:boolean (XML Schema 1.1 Part 2 section 3.3.2.2:
true, false, 1, 0) and denotes that boolean.  A rule applying them to
any other range is skipped with a warning: its RDF values are typed
literals or IRIs that equal no string.  Built-in type names resolve
without importing linkml:types, as in the main slot loop; the built-in
name of `curie` was misspelt there and is corrected.

Values are compared with `=`, spelled out as the disjunction SPARQL 1.1
section 17.4.1.9 defines `IN` to be, so the RDF 1.1-identical plain and
xsd:string literal forms both match and booleans compare by value;
rdflib evaluates `IN` and triple-pattern constants by term identity.
COALESCE turns the type error that RDFterm-equal raises for
incomparable literals into false, so a spec-conformant engine reports
such a value instead of dropping the row.  Queries are DISTINCT and
project ?path (and ?value where there is one), so each result names the
property and the offending value.  A value containing a backslash
followed by "u" or "U" is split with CONCAT, since codepoint escapes are
replaced before a query is parsed.

The exclusive-value pattern takes the precondition `has_member:
{equals_string: V}`, which states "V is one of the values". A bare
`equals_string: V` applies to every value of the slot, as the
specification applies a slot constraint to all members of a collection
and as gen-json-schema reads it, so it no longer matches this pattern:
such a rule is skipped with a warning naming has_member. The pattern
gets the same range check and value comparison, and its
maximum_cardinality > 1 form tests HAVING on the COUNT aggregate:
expressions projected by SELECT are not visible to HAVING (SPARQL 1.1
section 18.2.4.2), so `HAVING (?count > N)` never held and the
constraint never fired.

A rule applies to all members of its class, so a class shape now
carries the rules of its ancestors and mixins, as the JSON Schema
generator applies them.  Each rule is translated in the inheriting
class's context, where slot_usage may refine the slots it references.
Classes sharing a class_uri share one shape, which carries each rule
once.  With `open_world: true` "the postconditions may be omitted in
instance data", so an absent target is no violation.

Skip warnings name the rule by its position and its title, or its
description without one.

A rule whose conditions carry any operator beyond what a pattern
translates, or name an unknown or identifier slot, is skipped rather
than partially translated.  Each problem with a rule is logged once as a
warning naming the declaring class, the rule's position and the class
shapes it affects.  The metadata fields the operator accounting ignores
are derived from the metamodel.  Slot resolution goes through induced
slots, so slot_usage overrides, slot_uri overrides and alias-form keys
resolve to the IRI sh:path emits.

Behaviour changes for existing schemas: an exclusive-value rule with a
bare equals_string precondition is skipped (write has_member:
{equals_string: V}); the boolean guard rejects a string "true" on an
xsd:boolean flag and skips a flag whose type has another datatype IRI
(main compared with str()); exclusive-value rules with
maximum_cardinality > 1 now fire; inherited rules are now enforced on
subclass shapes; problems with rules are logged at WARNING instead of
DEBUG; rule results carry sh:resultPath and sh:value; sh:message follows
the rule's in_language or default_language.

Co-authored-by: jdsika <carlo.van-driesten@vdl.digital>
Signed-off-by: jdsika <carlo.van-driesten@vdl.digital>