Fix proofPurpose term definition.

Signed-off-by: Markus Sabadello <[email protected]>

Author: peacekeeper

src/main/resources/com/danubetech/verifiablecredentials/contexts/credentials-v1-CUSTOM.jsonld

@@ -92,7 +92,10 @@
 		},
 		"jws": "sec:jws",
 		"nonce": "sec:nonce",
-		"proofPurpose": "sec:proofPurpose",
+		"proofPurpose": {
+			"@id": "sec:proofPurpose",
+			"@type": "@vocab"
+		},
 		"assertionMethod": {
 			"@id": "sec:assertionMethod",
 			"@type": "@id",
@@ -123,7 +126,10 @@
 		},
 		"jws": "sec:jws",
 		"nonce": "sec:nonce",
-		"proofPurpose": "sec:proofPurpose",
+		"proofPurpose": {
+			"@id": "sec:proofPurpose",
+			"@type": "@vocab"
+		},
 		"proofValue": "sec:proofValue",
 		"verificationMethod": {
 			"@id": "sec:verificationMethod",
@@ -144,7 +150,10 @@
 		},
 		"jws": "sec:jws",
 		"nonce": "sec:nonce",
-		"proofPurpose": "sec:proofPurpose",
+		"proofPurpose": {
+			"@id": "sec:proofPurpose",
+			"@type": "@vocab"
+		},
 
 		"assertionMethod": {
 			"@id": "sec:assertionMethod",
@@ -175,7 +184,10 @@
 		},
 		"jws": "sec:jws",
 		"nonce": "sec:nonce",
-		"proofPurpose": "sec:proofPurpose",
+		"proofPurpose": {
+			"@id": "sec:proofPurpose",
+			"@type": "@vocab"
+		},
 		"assertionMethod": {
 			"@id": "sec:assertionMethod",
 			"@type": "@id",