Add a checklist for adding new types to EdgeDB (geldata#4373)

Author: msullivan

dev-notes/newtype-checklist.md

@@ -0,0 +1,51 @@
+This is a checklist of steps needed to add a new type to EdgeDB, along with links to examples of PRs doing the tasks.
+
+Core database range PRs:
+ * https://github.com/edgedb/edgedb/pull/3983
+ * https://github.com/edgedb/edgedb/pull/4020
+
+Core database cal::duration PRs:
+ * https://github.com/edgedb/edgedb/pull/3948
+
+- [ ] JSON handling
+  - [ ] Implement JSON casts if the default Postgres behavior won't work
+  - [ ] Update output.serialize_expr_to_json(), if the default won't work
+    * range: https://github.com/edgedb/edgedb/pull/4008
+
+- [ ] If any new functions or constructors have an implementation that is not
+      just purely a call to a strict function, make sure to test with inputs
+      that are NULL at runtime!
+      Probably the easiest way to generate NULL-at-runtime values is
+      `<optional TYPE>$0` and then passing in `{}`.
+  * range test example and bugfix: https://github.com/edgedb/edgedb/pull/4207/
+
+- [ ] For compound types, add a schema class in edb/schema/types.py and
+
+- [ ] Add mapping to pgsql types in edb/pgsql/types.py
+
+- [ ] Add implementations of any relevant functions/operations to `edb/lib`.
+
+- [ ] For compound types, add a type descriptor and code for encoding it in
+edb/server/compiler/sertypes.py.
+  * range: https://github.com/edgedb/edgedb/pull/4016
+
+- [ ] For new scalar types, add it to edb/api/types.txt and edb/graphql/types.py. Run `edb gen-types`.
+
+- [ ] Update all of the first-party language drivers (or get their owners to)
+  - [ ] Python (Fantix/Elvis/Sully)
+    * cal::date_duration: https://github.com/edgedb/edgedb-python/pull/335
+    * range: https://github.com/edgedb/edgedb-python/pull/332/
+  - [ ] Go (Frederick)
+    * cal::date_duration: https://github.com/edgedb/edgedb-go/pull/232
+  - [ ] Javascript (James/Colin)
+    * cal::date_duration: https://github.com/edgedb/edgedb-js/pull/373/
+    * range: https://github.com/edgedb/edgedb-js/pull/377
+  - [ ] Rust/CLI (Paul)
+    * This requires updating both the Rust bindings to support the
+      new type and the CLI to properly print it
+    * cal::date_duration: https://github.com/edgedb/edgedb-rust/pull/146, https://github.com/edgedb/edgedb-cli/pull/759
+    * range: https://github.com/edgedb/edgedb-rust/pull/145, https://github.com/edgedb/edgedb-cli/pull/755
+
+- [ ] Add a field of the new type to the `dump` test for the new version
+
+- [ ] Write tests.