use namespace for ca and rename CaState to ca::RequestState

Change-Id: I2250bf7fb68503465dae18e16dc3c512fe809037
diff --git a/src/identity-challenge/challenge-credential.cpp b/src/identity-challenge/challenge-credential.cpp
index 9cceefe..e4f21d4 100644
--- a/src/identity-challenge/challenge-credential.cpp
+++ b/src/identity-challenge/challenge-credential.cpp
@@ -75,7 +75,7 @@
 
 // For CA
 std::tuple<ErrorCode, std::string>
-ChallengeCredential::handleChallengeRequest(const Block& params, CaState& request)
+ChallengeCredential::handleChallengeRequest(const Block& params, ca::RequestState& request)
 {
   params.parse();
   if (m_trustAnchors.empty()) {