Added basic API endpoints (#258)

var/docs/README.md

@@ -13,12 +13,16 @@ For the most part Kimai usage should be self-explanatory, so we will only cover
 
 - [Timesheets](timesheet.md) - information about timesheets  
 
-## Developers and Administrators
+## Developer & Administrator
 
 - [Kimai configurations](configurations.md) - application configs, which can only be changed in config files 
 - [Developer docu](developers.md) - how to extend Kimai's feature set  
 - [User and Security](users.md) - docu for user and security topics, like authentication, registration and roles  
 - [FAQ](faq.md) - some answers to frequently asked questions 
+- [Emails](emails.md) - transport configuration and handling of emails 
+- [API](developers_api.md) - how to use the JSON API 
+
+## Installation
+ 
 - [Installation](installation.md) - instructions about several installation methods
 - [Importing data](migration_v1.md) - how to import your timesheets from Kimai v1
-- [Emails](emails.md) - transport configuration and handling of emails 

var/docs/developers_api.md

@@ -0,0 +1,23 @@
+# REST API
+
+Read the Swagger documentation of the Kimai 2 API in your Kimai installation at `/api/doc`.
+
+Or you can export the JSON collection by visiting `/api/doc.json`. Store the result in a file, which can be imported with Postman.
+
+## Authentication
+
+When calling the API you have to submit two additional header with every call for authentication:
+
+- `X-AUTH-USER` - holds the username or email
+- `X-AUTH-TOKEN` - holds the users API password, which he can set in his profile
+
+Please make sure to ONLY call the Kimai 2 API via `https` to protect the users data!
+
+## Calling the API with Javascript
+
+If you develop your own extension and need to use the API for logged-in user, then you have to set the header `X-AUTH-SESSION` 
+which will allow Kimai to use the current user session and not look for the default token based API authentication.
+
+### Next step
+
+Back to the [developer documentation](developers.md).

var/docs/internal.md

@@ -10,3 +10,4 @@ Internal documentation for project maintainers
 - Push a release branch and add it as last PR merge into master
 - Edit the release-draft and add the "Full changelog" link + everything from the "Merged pull requests" section from CHANGELOG.md
 - Create the release
+- Post a new issue at [YunoHost tracker for Kimai 2](https://github.com/YunoHost-Apps/kimai2_ynh)