templates: one Jinja language (hive-template) for the notify router's flows, flows document version 2

A todo node's key and text were hand-expanded `{field}` strings. They are now Jinja templates rendered through the new hive-template crate (minijinja, an unknown variable is an error), and the controller's save check reads the variables the template uses. The flows document is version 2; a version 1 document reads as version 2 with each `{field}` converted to `{{ field }}`, and the next save writes it.

Cargo.lock

@@ -2106,6 +2106,15 @@ dependencies = [
  "uuid",
 ]
 
+[[package]]
+name = "hive-template"
+version = "0.1.0"
+dependencies = [
+ "minijinja",
+ "serde",
+ "serde_json",
+]
+
 [[package]]
 name = "hive-types"
 version = "0.1.0"
@@ -3176,6 +3185,12 @@ version = "2.8.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cf8baf1c55e62ffcace7a9f06f4bd9cd3f0c4beb022d3b367256b91b87513d98"
 
+[[package]]
+name = "memo-map"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5449c8c750f1a07ea702bbd212bd999fceece9b3d1508b17023b3e174583124b"
+
 [[package]]
 name = "mime"
 version = "0.3.18"
@@ -3198,6 +3213,16 @@ dependencies = [
  "unicase",
 ]
 
+[[package]]
+name = "minijinja"
+version = "2.24.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "86886cf6dbf4e614b19c9a1eec9775f021869d7eadde0fc73921a81b90c9b4c9"
+dependencies = [
+ "memo-map",
+ "serde",
+]
+
 [[package]]
 name = "miniz_oxide"
 version = "0.9.1"
@@ -5254,6 +5279,7 @@ dependencies = [
  "async-nats",
  "futures-util",
  "hive-log",
+ "hive-template",
  "opentelemetry",
  "opentelemetry_sdk",
  "serde",
@@ -5338,6 +5364,7 @@ dependencies = [
 name = "swarm-wire"
 version = "0.1.0"
 dependencies = [
+ "hive-template",
  "hive-types",
  "serde",
  "serde_json",