chore(monorepo): put back docs

docs/User Guide/User Guide/Advanced Usage/ETAPI (REST API).md

@@ -0,0 +1,64 @@
+# ETAPI (REST API)
+ETAPI is Trilium's public/external REST API. It is available since Trilium v0.50.
+
+The documentation is in OpenAPI format, available [here](https://github.com/TriliumNext/Notes/blob/master/src/etapi/etapi.openapi.yaml).
+
+## API clients
+
+As an alternative to calling the API directly, there are client libraries to simplify this
+
+*   [trilium-py](https://github.com/Nriver/trilium-py), you can use Python to communicate with Trilium.
+
+## Obtaining a token
+
+All operations with the REST API have to be authenticated using a token. You can get this token either from Options -> ETAPI or programmatically using the `/auth/login` REST call (see the [spec](https://github.com/TriliumNext/Notes/blob/master/src/etapi/etapi.openapi.yaml)).
+
+## Authentication
+
+### Via the `Authorization` header
+
+```
+GET https://myserver.com/etapi/app-info
+Authorization: ETAPITOKEN
+```
+
+where `ETAPITOKEN` is the token obtained in the previous step.
+
+For compatibility with various tools, it's also possible to specify the value of the `Authorization` header in the format `Bearer ETAPITOKEN` (since 0.93.0).
+
+### Basic authentication
+
+Since v0.56 you can also use basic auth format:
+
+```
+GET https://myserver.com/etapi/app-info
+Authorization: Basic BATOKEN
+```
+
+*   Where `BATOKEN = BASE64(username + ':' + password)` - this is a standard Basic Auth serialization
+*   Where `username` is "etapi"
+*   And `password` is the generated ETAPI token described above.
+
+Basic Auth is meant to be used with tools which support only basic auth.
+
+## Interaction using Bash scripts
+
+It is possible to write simple Bash scripts to interact with Trilium. As an example, here's how to obtain the HTML content of a note:
+
+```
+#!/usr/bin/env bash
+
+# Configuration
+TOKEN=z1vA4fkGxjOR_ZXLrZeqHEFOv65yV3882iFCRtNIK9k9iWrHliITNSLQ=
+SERVER=http://localhost:8080
+
+# Download a note by ID
+NOTE_ID="i6ra4ZshJhgN"
+curl "$SERVER/etapi/notes/$NOTE_ID/content" -H "Authorization: $TOKEN" 
+```
+
+Make sure to replace the values of:
+
+*   `TOKEN` with your ETAPI token.
+*   `SERVER` with the correct protocol, host name and port to your Trilium instance.
+*   `NOTE_ID` with an existing note ID to download.