update new documentation and move to doc/

doc/developers-guide/plugin-development/json-rpc-passthrough.md

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+---
+title: "JSON-RPC passthrough"
+slug: "json-rpc-passthrough"
+hidden: false
+createdAt: "2023-02-03T08:53:50.840Z"
+updatedAt: "2023-02-03T08:53:50.840Z"
+---
+Plugins may register their own JSON-RPC methods that are exposed through the JSON-RPC provided by `lightningd`. This provides users with a single interface to interact with, while allowing the addition of custom methods without having to modify the daemon itself.
+
+JSON-RPC methods are registered as part of the `getmanifest` result. Each registered method must provide a `name` and a `description`. An optional `long_description` may also be  
+provided. This information is then added to the internal dispatch table, and used to return the help text when using `lightning-cli
+help`, and the methods can be called using the `name`.
+
+For example, `getmanifest` result will register two methods, called `hello` and `gettime`:
+
+```json
+  ...
+  "rpcmethods": [
+    {
+      "name": "hello",
+      "usage": "[name]",
+      "description": "Returns a personalized greeting for {greeting} (set via options)."
+    },
+    {
+      "name": "gettime",
+      "description": "Returns the current time in {timezone}",
+      "usage": "",
+      "long_description": "Returns the current time in the timezone that is given as the only parameter.\nThis description may be quite long and is allowed to span multiple lines."
+    }
+  ],
+  ...
+```
+
+
+
+The RPC call will be passed through unmodified, with the exception of the JSON-RPC call `id`, which is internally remapped to a unique integer instead, in order to avoid collisions. When passing the result back the `id` field is restored to its original value.
+
+Note that if your `result` for an RPC call includes `"format-hint":
+"simple"`, then `lightning-cli` will default to printing your output in "human-readable" flat form.