Merge pull request #100 from adorsys/94-create-a-readme-file-for-did-…

…endpoint

Creation of the did-endpoint documentation

did-endpoint/README.md

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+# did-endpoint 
+## Overview
+The `did-endpoint` is a robust, flexible, and extendable framework for managing Decentralized Identifiers (DIDs)
+
+## Purpose
+The DID endpoint aims to simplify the management of Decentralized Identifiers (DIDs) by providing a decentralized service that supports multiple DID methods.
+
+## Features 
+- **Turns an HTTP(S) URL into a did:web id:** 
+- **Generates keys and forward them for DID generation:**
+- **Builds and persists DID document:**
+- **Proof of Possession:**
+
+## Usage
+- **Turns an HTTP(S) URL into a did:web id:** 
+```rust
+        //This is a function call to url_to_did_web_id with the argument "localhost:8080".
+        //"localhost:8080" is the URL that you want to convert into a did:web identifier.
+            url_to_did_web_id("localhost:8080")?,
+        //This is the expected output, which is the did:web identifier corresponding to the given URL
+            "did:web:localhost%3A8080",
+```
+- **Generates keys and forward them for DID generation::**
+```rust
+let authentication_key = Jwk {
+            key: Key::Okp(Okp {
+                crv: OkpCurves::Ed25519,
+                x: Bytes::from(
+                    String::from(
+                        "d75a980182b10ab2463c5b1be1b4d97e06ec21ebac8552059996bd962d77f259",
+                    )
+                    .into_bytes(),
+                ),
+                d: None,
+            }),
+            prm: Parameters::default(),
+        };
+
+let assertion_key = Jwk {
+        key: Key::Okp(Okp {
+            crv: OkpCurves::Ed25519,
+            x: Bytes::from(
+                String::from(
+                    "d75a980182b10ab2463c5b1be1b4d97e06ec21ebac8552059996bd962d77f259",
+                )
+                .into_bytes(),
+            ),
+                d: None,
+            }),
+            prm: Parameters::default(),
+        };
+
+let agreement_key = Jwk {
+        key: Key::Okp(Okp {
+            crv: OkpCurves::X25519,
+            x: Bytes::from(
+                String::from(
+                    "d75a980182b10ab2463c5b1be1b4d97e06ec21ebac8552059996bd962d77f259",
+                )
+                .into_bytes(),
+            ),
+            d: None,
+        }),
+        prm: Parameters::default(),
+    }
+let diddoc = gen_diddoc(
+            &storage_dirpath,
+            &server_public_domain,
+            authentication_key.clone(),
+            assertion_key.clone(),
+            agreement_key.clone(),
+        )
+```
+- **Builds and persists DID document:**
+```rust
+let expected_verification_methods = vec![
+        VerificationMethod {
+            id: "did:web:example.com#keys-1".to_string(),
+            public_key: Some(KeyFormat::Jwk(authentication_key)),
+            ..VerificationMethod::new(
+                "did:web:example.com#keys-1".to_string(),
+                String::from("JsonWebKey2020"),
+                "did:web:example.com".to_string(),
+            )
+        },
+        VerificationMethod {
+            id: "did:web:example.com#keys-2".to_string(),
+            public_key: Some(KeyFormat::Jwk(assertion_key)),
+            ..VerificationMethod::new(
+                "did:web:example.com#keys-2".to_string(),
+                String::from("JsonWebKey2020"),
+                "did:web:example.com".to_string(),
+            )
+        },
+        VerificationMethod {
+            id: "did:web:example.com#keys-3".to_string(),
+            public_key: Some(KeyFormat::Jwk(agreement_key)),
+            ..VerificationMethod::new(
+                "did:web:example.com#keys-3".to_string(),
+                String::from("JsonWebKey2020"),
+                "did:web:example.com".to_string(),
+            )
+        },
+    ]
+```
+- ## **Proof of Possession:**
+- **Challenge Handling:**
+    Retrieves a challenge from incoming query parameters to initiate PoP.
+- **Key Store Retrieval:**
+
+    Fetches cryptographic keys from a specified storage directory (STORAGE_DIRPATH) to sign and verify proofs.
+- **DID Document and Verification Methods:**
+
+    Loads the DID document and its associated verification methods, which contain public keys for cryptographic operations.
+- **Verifiable Credential (VC) Construction:**
+
+    Constructs a Verifiable Credential (VC) using the DID document, indicating it as a type of Verifiable Credential and DID Document.
+- **Verifiable Presentation (VP) Creation:**
+
+    Constructs a Verifiable Presentation (VP) containing the VC and other necessary metadata, such as context and ID.
+- **Proof of Possession Generation:**
+
+    Generates proofs of possession for each verification method listed in the DID document.
+    Uses cryptographic keys to sign the challenge and embeds these proofs into the VP.
+- **Output:**
+
+    Returns the final VP with embedded proofs as a JSON response 
+