Add a binary for generating the OpenAPI schema for the metadata type. (#453)

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## Description

I needed this, so I made it. It's nothing too complex: we just
pretty-print the `schemars` schema for the root `Metadata` type.

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### Product
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- [ ] community-edition
- [ ] cloud
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V3_GIT_ORIGIN_REV_ID: a9e75bfa06c35577c17d8cbf0d021b1f56826a28

v3/Cargo.lock

@@ -1798,6 +1798,15 @@ dependencies = [
  "autocfg",
 ]
 
+[[package]]
+name = "metadata-schema-generator"
+version = "0.1.0"
+dependencies = [
+ "open-dds",
+ "schemars",
+ "serde_json",
+]
+
 [[package]]
 name = "mime"
 version = "0.3.17"

v3/crates/metadata-schema-generator/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "metadata-schema-generator"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+open-dds = { path = "../open-dds" }
+serde_json = "1.0.92"
+schemars = { version = "0.8.12", features = ["smol_str"] }

v3/crates/metadata-schema-generator/README.md

@@ -0,0 +1,9 @@
+# Metadata Schema Generator
+
+When we make changes to the metadata schema, we need to regenerate the
+goldenfile to make the tests happy. We can use the following command to get the
+schema immediately for whatever reason:
+
+```bash
+$ cargo run --bin metadata-schema-generator
+```

v3/crates/metadata-schema-generator/src/main.rs

@@ -0,0 +1,8 @@
+use open_dds::traits::gen_root_schema_for;
+use open_dds::Metadata;
+use schemars::gen::SchemaGenerator;
+
+fn main() {
+    let schema = gen_root_schema_for::<Metadata>(&mut SchemaGenerator::default());
+    println!("{}", serde_json::to_string_pretty(&schema).unwrap());
+}