Added documentation for OAuth login

Kobo-Integration.md

@@ -6,6 +6,7 @@ I'd recommend waiting a little bit for this cautionary message do disappear if y
 * [#1276](../../issues/1276) : Syncing of large libraries may timeout and fail.
 
 ## Setup
+As prerequiste you need to install the dependencies listed in optional-requirements.txt in the Kobo integration section. 
 Kobo integration must first be enabled in Calibre-Web by toggling ON the **Enable Kobo sync** checkbox in the **Basic configuration >> Feature Configuration** page.
 
 The **Kobo eReader.conf** file found under the **.kobo** directory on Kobo devices is used to configure which URL the device uses for syncing books. By default, the config file contains the following row:

OAuth-Login-with-Github-and-Google.md

@@ -1 +1,24 @@
-### Github Login
+## Setup
+
+As prerequiste you need to install the dependencies listed in optional-requirements.txt in the Kobo integration section. 
+
+### Setup Github as Oauth provider
+The server hosting Calibre-Web has to be accessible via Internet to use this feature.
+Enable the OAuth login in Admin section -> Basic configuration -> Feature Configuration. You will see 2 new configuration fields poping up, and a link for creating the necessary settings on Github.
+After following the link, please create a new OAuth application by clicking on "New OAuth app".
+The following screenshot shows the relevant settings.
+
+![Settings](images/OAuth/Github_OAuth_Settings.png)
+
+The callbackroutine has to end with `login/github/authorized`.
+After clicking on "Register application" Github will present you the Client ID and Client secret values. 
+
+![Keys](images/OAuth/Github_Keys.png)
+
+Please enter both values in the corresponding fields in Calibre-Web. After pressing save, the OAuth login is ready to use.
+Each user has afterwards to link his Github account to Calibre-Web. This is done by going to the user's profile page. There you see a "Link" Buttn, by clicking on this, you will redirect to Github, where you are asked to enter your Github username and Github password. Github will now redirect you back to Calibre-Web and the buttons text changes to "Unlink". 
+By clicking on "Unlink" you remove the Github account from your user's account and it's no longer possible to login to this user with the Github account.
+
+If you log out from Calibre-Web, you will see a little Github account on the login page, by clicking the logo, you will redirect to Github. By entering a Github username and Github password you are logged in to the corresponding linked Calibre-Web user.
+
+### Setup Google as Oauth provider