Updated external_access md for use-case partners

minimalistic docu for use-case partners to use our most important endpoints

documentation/external_access.md

 # SMART RESTful API Gateway
+https://articonf1.itec.aau.at:30401/api/ui/ 
 
+The API Gateway serves as an interface to external applications. Here, users are authenticated and blockchain transactions are added.
+
+## Authentication
+```POST https://articonf1.itec.aau.at:30401/api/tokens``` with body:
+```
+{
+  "username":"regular@itec.aau.at",
+  "password":"2bViezK0Tst2LzsTIXix"
+}
+```
+returns the JWT token for authentication, e.g. 
+```
+{
+  "token": "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9..."
+}
+```
+This token is used for authentication as _regular user_ on all microservices currently supporting authentication. Therefore the authentication header "```Bearer eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9...```" has to be added to the request.
+
+## Blockchain transactions
 ```POST https://articonf1.itec.aau.at:30401/api/trace``` with body:
 ```
 {
@@ -16,14 +36,21 @@ https://articonf1.itec.aau.at:30420/api/ui
 This microservice contains use-case specific informations, like schemas and contexts.
 
 ## Schema information
-```GET https://articonf1.itec.aau.at:30420/api/use-cases/{use-case}/schema``` returns all schema mappings for the use-case identifier. The mapping is used to flatten nested input from the blockchain.
+```GET https://articonf1.itec.aau.at:30420/api/use-cases/{use-case}/tables``` returns all schema mappings for the use-case identifier. The mapping is used to flatten nested input from the blockchain.
 
 ## Context information
 ```GET https://articonf1.itec.aau.at:30420/api/use-cases/{use-case}/layers``` returns all layers from the schema used for clustering interally.
 
+# Semantic Linking Microservice
+https://articonf1.itec.aau.at:30101/api/ui/
+
+This microservice contains the nodes from the transactions preprocessed as defined in *Schema Information*. Additionally it splits the raw input into multipe layers.
+
+```GET https://articonf1.itec.aau.at:30101/api/use-cases/{use-case}/nodes``` returns all preprocessed transactions, called nodes, before splitting them into layers.
+
 # Role Stage Discovery Microservice
 https://articonf1.itec.aau.at:30103/api/ui
 
-This microservice contains the communities based on clusters and similarities between communities.
+This microservice contains the communities based on clusters and similarities between communities. It additionally contains time slices with subsets of clusters, which's transaction happened in the corresponding time.
 
-The endpoints are currently refactored, I will describe them once we are finished and processed data is available.
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+The endpoints are currently refactored, so please check the Swagger UI autogenerated documentation on its website.
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