Update documentation to include privacy note.

CONTRIBUTING.md

@@ -1,4 +0,0 @@
-# Contributing
-
-## TODOs:
-- [ ] Validate webhook signature

README.md

@@ -2,6 +2,9 @@
 
 This project allows you to automatically categorize your expenses by using OpenAI.
 
+
+## How it works
+
 It provides a webhook that you can set up to be called every time a new expense is added.
 
 It will then generate a prompt for OpenAI, including your existing categories, the recipient and the description of the
@@ -14,6 +17,16 @@ transaction.
 
 If it cannot detect the category, it will not update anything.
 
+
+## Privacy
+Please note that some details of the transactions will be sent to OpenAI as information to guess the category.
+
+These are:
+- Transaction description
+- Name of transaction destination account
+- Names of all categories
+
+
 ## Installation
 
 ### 1. Get a Firefly Personal Access Token
@@ -105,6 +118,7 @@ categorization everytime a new transaction comes in.
 
 Now you are ready and every new withdrawal transaction should be automatically categorized by OpenAI.
 
+
 ## User Interface
 
 The application comes with a minimal UI that allows you to monitor the classification queue and see the OpenAI prompts
@@ -115,6 +129,7 @@ To enable this UI set the environment variable `ENABLE_UI` to `true`.
 After a restart of the application the UI can be accessed at `http://localhost:3000/` (or any other URL that allows you
 to reach the container).
 
+
 ## Adjust Tag name
 
 The application automatically sets the tag "AI categorized" on every transaction that was processed and a category could
@@ -122,10 +137,12 @@ be guessed.
 
 You can configure the name of this tag by setting the environment variable `FIREFLY_TAG` accordingly.
 
+
 ## Running on a different port
 
 If you have to run the application on a different port than the default port `3000` set the environment variable `PORT`.
 
+
 ## Full list of environment variables
 
 - `FIREFLY_URL`: The URL to your Firefly III instance. Example: `https://firefly.example.com`. (required)