feat(subscriptions): add cmd to gen json schema

This commit introduces the 'notification-schema' command to generate a
JSON schema of the Notification struct which gets sent when notifying
subscribers of updates.

Cargo.lock

@@ -229,6 +229,12 @@ dependencies = [
  "winapi 0.3.9",
 ]
 
+[[package]]
+name = "dyn-clone"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ee2626afccd7561a06cf1367e2950c4718ea04565e20fb5029b6c7d8ad09abcf"
+
 [[package]]
 name = "either"
 version = "1.6.1"
@@ -462,6 +468,7 @@ dependencies = [
  "nanoid",
  "parking_lot",
  "paste",
+ "schemars",
  "serde",
  "serde_json",
  "strum",
@@ -482,6 +489,7 @@ version = "0.1.8"
 dependencies = [
  "clap",
  "color-eyre",
+ "schemars",
  "serde",
  "serde_json",
  "serde_yaml",
@@ -1029,6 +1037,30 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "schemars"
+version = "0.8.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c6b5a3c80cea1ab61f4260238409510e814e38b4b563c06044edf91e7dc070e3"
+dependencies = [
+ "dyn-clone",
+ "schemars_derive",
+ "serde",
+ "serde_json",
+]
+
+[[package]]
+name = "schemars_derive"
+version = "0.8.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "41ae4dce13e8614c46ac3c38ef1c0d668b101df6ac39817aebdaa26642ddae9b"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "serde_derive_internals",
+ "syn",
+]
+
 [[package]]
 name = "scopeguard"
 version = "1.1.0"
@@ -1055,6 +1087,17 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "serde_derive_internals"
+version = "0.25.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1dbab34ca63057a1f15280bdf3c39f2b1eb1b54c17e98360e511637aef7418c6"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "serde_json"
 version = "1.0.78"