Implement Open RPC specification for API

### Is your feature request related to a problem?

Since we swithed ou APIs from REST to JSON RPC, we should use a standardized way to format and expose those API.
We can do this by using the [Open RPC](https://open-rpc.org/) specification.

### Describe the solution you'd like

We need to create a new Open RPC document and respect all the required specification.

This require to use JSON Schema over Ecto for validating request format / data.

Currently there is no easy way to manage OpenRPC document in Elixir. We could create a new library to validate and build OpenRPC document.

### Additional context

Open RPC created a [playground](https://playground.open-rpc.org/) to help users exploring the APIs and testing them (like Swagger).
There is a plugin for docusaurus to integrate the playground into the documentation : https://github.com/MetaMask/docusaurus-openrpc

### Epic

_No response_

Start by reviewing the existing JSON RPC APIs and the Open RPC specification linked in the issue, then compare the proposed JSON Schema-over-Ecto validation with the OpenRPC playground. The work is done when a compliant OpenRPC document and a clear approach for validating request format and data are established for the API.

Written by the indexing model from the issue text.