Factor out thing and prov schema

I believe at this point that the basic concept works. It now made sense
to cut the large schema up into pieces to make them more digestible, and
possible allow for leaner selections (later).

We now have

- `thing`: the base building block (describe a thing)
- `prov`: describe what happened to a thing and how it relates to other
  things
- `distribution`: a generic "frontend" schema
- `sdd` (science data distribution): a tailored frontend schema

Few other changes were made:

- schemas include each other by relative identifier (avoids having to
  update an online schema first, before changes can be used in derived
  schemas)
- Examples have been shifted to their most relevant schema, but they
  continue to be executed as validation tests for others

Makefile

@@ -14,6 +14,8 @@ try:
 all: build/mkdocs-site
 
 build/linkml-docs: \
+	build/linkml-docs/s/thing/unreleased \
+	build/linkml-docs/s/prov/unreleased \
 	build/linkml-docs/s/distribution/unreleased \
 	build/linkml-docs/s/sdd/unreleased
 build/linkml-docs/s/%: src/%.yaml src/%/extra-docs
@@ -39,6 +41,8 @@ check: check-models check-validation
 
 # add additional schemas to lint here
 check-models: \
+	checkmodel/thing/unreleased \
+	checkmodel/prov/unreleased \
 	checkmodel/distribution/unreleased \
 	checkmodel/sdd/unreleased
 checkmodel/%: src/%.yaml
@@ -67,6 +71,10 @@ checkmodel/%: src/%.yaml
 # respective validation targets, because some tests rely on these
 # converted formats
 check-validation: \
+	convertexamples/thing/unreleased \
+	checkvalidation/thing/unreleased \
+	convertexamples/prov/unreleased \
+	checkvalidation/prov/unreleased \
 	convertexamples/distribution/unreleased \
 	checkvalidation/distribution/unreleased \
 	convertexamples/sdd/unreleased \
@@ -85,6 +93,8 @@ checkinvalid/%: src/%/validation src/%.yaml
 	done
 
 convert-examples: \
+	convertexamples/thing/unreleased \
+	convertexamples/prov/unreleased \
 	convertexamples/distribution/unreleased \
 	convertexamples/sdd/unreleased
 convertexamples/%: src/%.yaml src/%/examples

mkdocs.yml

@@ -4,8 +4,9 @@ nav:
   - Home: index.md
   - About: about.md
   - Schemas:
+    - Thing (unreleased): s/thing/unreleased/index.md
+    - Provenance (unreleased): s/prov/unreleased/index.md
     - Distribution (unreleased): s/distribution/unreleased/index.md
-    - Demo derived schema: s/derived-example/unreleased/index.md
 plugins:
   - mermaid2
   - redirects: