Merge pull request eclipse-tractusx#581 from catenax-ng/feature/TRI-1…

…604-concept-EDR-cache-and-reuse

feat(docs):[TRI-1604] Add concept for EDR caching and reuse

docs/concept/EDR-Token-Cache-and-reuse.md

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+# \[Concept\] \[TRI-1604\] EDC EDR Token negotiation and usage
+
+## Glossary
+
+| Abbreviation | Name                         |
+|--------------|------------------------------|
+| EDR          | EndpointDataReference        |
+| EDR-Storage  | EndpointDataReferenceStorage |
+
+## Existing flow - single use token
+
+The existing flow of token negotiation and usage only allows to use a negotiated contract and the resulting EDR (
+Endpoint Data Reference) Token to be used once.
+After the token is consumed, it is removed from the EDR-Storage (EndpointDataReferenceStorage).
+
+```mermaid
+sequenceDiagram
+    autonumber
+    participant EdcSubmodelClient
+    participant ContractNegotiationService
+    participant EndpointDataReferenceStorage
+    participant EdcCallbackController
+    participant EdcDataPlaneClient
+    EdcSubmodelClient ->> ContractNegotiationService: Negotiate new EDR Token
+    ContractNegotiationService -->> EdcCallbackController: EDC flow
+    EdcCallbackController ->> EndpointDataReferenceStorage: Store EDR token by contract agreement id after EDC callback
+    loop While EDR Token is not present
+        EdcSubmodelClient ->> EndpointDataReferenceStorage: Poll for EDR Token
+    end
+    EndpointDataReferenceStorage ->> EdcSubmodelClient: Return EDR Token
+    EdcSubmodelClient ->> EdcDataPlaneClient: Get data(EDR Token, Dataplane URL)
+    EdcDataPlaneClient ->> EdcSubmodelClient: Return data
+```
+
+## New flow - reuse token
+
+To increase performance for assets with the same EDC contract, IRS should be able to reuse an existing EDR token.
+
+To make this possible, two things have to be adjusted.
+
+1. IRS has to check first, if an EDR Token for the requested EDC Asset ID is available in EDR-Storage
+2. EDR Tokens have to be stored in the EDR-Storage with the EDC Asset ID as key instead of contract agreement id
+
+```mermaid
+sequenceDiagram
+    autonumber
+    participant EdcSubmodelClient
+    participant ContractNegotiationService
+    participant EndpointDataReferenceStorage
+    participant EdcCallbackController
+    participant EdcDataPlaneClient
+    EdcSubmodelClient ->> EndpointDataReferenceStorage: Get EDR Token for EDC asset id
+    EndpointDataReferenceStorage ->> EdcSubmodelClient: Return Optional<EDR Token>
+    alt Token is present and not expired
+        EdcSubmodelClient ->> EdcSubmodelClient: Optional.get
+    else
+        alt Token is expired
+            EdcSubmodelClient ->> ContractNegotiationService: Renew EDR Token based on existing Token
+        else Token is not present
+            EdcSubmodelClient ->> ContractNegotiationService: Negotiate new EDR Token
+        end
+        ContractNegotiationService -->> EdcCallbackController: EDC flow
+        EdcCallbackController ->> EndpointDataReferenceStorage: Store EDR token by EDC asset id after EDC callback
+        loop While EDR Token is not present
+            EdcSubmodelClient ->> EndpointDataReferenceStorage: Poll for EDR Token
+        end
+        EndpointDataReferenceStorage ->> EdcSubmodelClient: Return EDR Token
+    end
+    EdcSubmodelClient ->> EdcDataPlaneClient: Get data(EDR Token, Dataplane URL)
+    EdcDataPlaneClient ->> EdcSubmodelClient: Return data
+```
+
+### Case: Token already present in EDR-Storage
+
+```mermaid
+flowchart LR
+    A[EDR Token] --> B[extract authCode]
+    B --> C[decode JWT]
+    C --> D[get expiry date 'exp']
+    D --> E{isAvailable}
+    E -->|Yes| F{isValid}
+    E -->|No| H[Request new Token]
+    F -->|Yes| G{isExpired}
+    F -->|No| H
+    G -->|Yes| H
+    G -->|No| I[Reuse Token]
+```
+
+### Case: Token is expired
+
+```mermaid
+sequenceDiagram
+    autonumber
+    participant EdcSubmodelClient
+    participant ContractNegotiationService
+    participant EndpointDataReferenceStorage
+    participant EdcCallbackController
+    EdcSubmodelClient ->> EdcSubmodelClient: extract contract agreement ID 'cid' from Token authCode
+    EdcSubmodelClient ->> ContractNegotiationService: start transfer process(EDC asset ID, cid, connector URL, connector ID)
+    ContractNegotiationService -->> EdcCallbackController: EDC flow
+    EdcCallbackController ->> EndpointDataReferenceStorage: Store EDR token by EDC asset id after EDC callback
+    loop While EDR Token is not present
+        EdcSubmodelClient ->> EndpointDataReferenceStorage: Poll for EDR Token
+    end
+    EndpointDataReferenceStorage ->> EdcSubmodelClient: Return EDR Token
+```