fix: Small improvement to returning "issuer" from VC 2.0

Author: peacekeeper

src/main/java/com/danubetech/verifiablecredentials/VerifiableCredentialV2.java

@@ -245,12 +245,17 @@ public static void removeFromJsonLdObject(JsonLDObject jsonLdObject) {
 	 */
 
 	public Object getIssuer() {
-		return JsonLDUtils.jsonLdGetJsonValue(this.getJsonObject(), VerifiableCredentialKeywords.JSONLD_TERM_ISSUER);
+		Object issuer = JsonLDUtils.jsonLdGetJsonValue(this.getJsonObject(), VerifiableCredentialKeywords.JSONLD_TERM_ISSUER);
+		if (issuer instanceof String issuerString) return JsonLDUtils.stringToUri(issuerString);
+        if (issuer instanceof Map<?, ?> issuerMap) return issuerMap;
+		return null;
 	}
 
 	public URI getIssuerUri() {
 		Object issuer = JsonLDUtils.jsonLdGetJsonValue(this.getJsonObject(), VerifiableCredentialKeywords.JSONLD_TERM_ISSUER);
-		return (issuer instanceof String) ? URI.create(issuer.toString()) : URI.create((((Map<String,Object>)issuer).get(VerifiableCredentialKeywords.JSONLD_TERM_ISSUER)).toString());
+		if (issuer instanceof String issuerString) return JsonLDUtils.stringToUri(issuerString);
+		if (issuer instanceof Map<?, ?> issuerMap) return JsonLDUtils.stringToUri((String) issuerMap.get(VerifiableCredentialKeywords.JSONLD_TERM_ISSUER));
+		return null;
 	}
 
 	public Date getValidFrom() {

src/main/java/com/danubetech/verifiablecredentials/validation/Validation.java

@@ -112,7 +112,7 @@ public static void validate(VerifiablePresentationV2 verifiablePresentation, boo
     private static void validateIssuer(VerifiableCredentialV2 verifiableCredential) throws IllegalStateException {
 
         validateRun(() -> validateTrue(verifiableCredential.getIssuer() != null), "Bad or missing 'issuer'.");
-        if (verifiableCredential.getIssuer() instanceof String issuerString) validateRun(() -> validateUrl(URI.create(issuerString)), "'issuer' must be a valid URI.");
+        if (verifiableCredential.getIssuer() instanceof URI issuerUri) validateRun(() -> validateUrl(issuerUri), "'issuer' must be a valid URI.");
         else if (verifiableCredential.getIssuer() instanceof Map<?,?> issuerMap) validateRun(()-> validateUrl(URI.create(((Map<String,Object>) issuerMap).get("id").toString())), "'issuer' must contain be a valid 'id'.");
         else validateRun(() -> validateTrue(false),"'issuer' must be a valid URI or object containing an 'id' property.");
     }