Merge branch 'add-publikKeysForDIDs-policy' into 'main'

Add publicKeysForDIDs policy

See merge request !18

example/publicKeysForDIDs/1.0/data.json

+{
+  "dids": [
+    "did:key:z6MkpxjNepTaD1xo49dEbbW36FguWgsiToxNdhR8YJMnFQoJ",
+    "did:key:z6Mkfriq1MqLBoPWecGoDLjguo1sB9brj6wT3qZ5BxkKpuP6"
+  ]
+}
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example/publicKeysForDIDs/1.0/policy.rego

+package example.publicKeysForDIDs
+
+publicKeys := getKeys(input)
+
+getKeys(i) = res {
+	doc1 = did.resolve(data.dids[0])
+	doc2 = did.resolve(data.dids[1])
+	res := array.concat([doc1.didDocument.verificationMethod[0].publicKeyMultibase], [doc2.didDocument.verificationMethod[0].publicKeyMultibase])
+}
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