first update of readme

Reviewed-by: Gode, Sebastian <sebastian.gode@t-systems.com>
Co-authored-by: tischrei <tino.schreiber@t-systems.com>
Co-committed-by: tischrei <tino.schreiber@t-systems.com>

README.rst

@@ -1,6 +1,9 @@
-===============================
+============
-ssh://git@gitea.eco.tsi-dev.otc-service.com:2222/infra/otc-metadata.git
+otc-metadata
-===============================
+============
+
+Link: ssh://git@gitea.eco.tsi-dev.otc-service.com:2222/infra/otc-metadata.git
+
 
 Metadata about OTC for Ecosystem
 
@@ -13,6 +16,39 @@ Note that this is a hard requirement.
 * Source: https://github.com/infra/ssh://git@gitea.eco.tsi-dev.otc-service.com:2222/infra/otc-metadata.git
 
 Features
---------
+========
 
 * TODO
+
+Overview: service.yaml
+======================
+
+The :code:`service.yaml` file contains all data about services, service
+categories and the related documents of each service. The file is
+used as a base for several internal and external applications or
+websites like the Helpcenter 3.0 where the information about the document
+repositories and its properties are stored.
+
+File structure
+--------------
+
+The file is based on the yaml-file format and has three main sections
+which can be compared with database tables in a relational database.
+
+* documents: contains the information about every single document and its type
+  like umn, api-ref etc.
+
+* service category: contains the keyword and title of the service category
+
+* services: contains the repository information about the internal (Gitea) and
+  external location (GitHub) and all the necessary parameters of the service itself
+
+These sections, or better "tables" have
+their own keys and foreign keys so that the tables are linked together and
+the related information can be fetched.
+For the :code:`services` table
+the key is :code:`service_type` which has the foreign key in the
+:code:`documents` table. So a service can have multiple documents and each
+document can only be linked to one service.
+The key :code:`service_category` table is :code:`name` of the service category
+which is then used in the :code:`services` table as foreign key.