User Discovery Environment

• Add UDEnvironment struct that wraps ud address, cert, and contact into a single model.
• Use UDEnvironment in XXMessengerClient

.swiftpm/xcode/xcshareddata/xcschemes/elixxir-dapps-sdk-swift-Package.xcscheme

@@ -36,10 +36,10 @@
          </BuildActionEntry>
          <BuildActionEntry
             buildForTesting = "YES"
-            buildForRunning = "YES"
+            buildForRunning = "NO"
             buildForProfiling = "NO"
             buildForArchiving = "NO"
-            buildForAnalyzing = "YES">
+            buildForAnalyzing = "NO">
             <BuildableReference
                BuildableIdentifier = "primary"
                BlueprintIdentifier = "XXClientTests"
@@ -50,10 +50,10 @@
          </BuildActionEntry>
          <BuildActionEntry
             buildForTesting = "YES"
-            buildForRunning = "YES"
+            buildForRunning = "NO"
             buildForProfiling = "NO"
             buildForArchiving = "NO"
-            buildForAnalyzing = "YES">
+            buildForAnalyzing = "NO">
             <BuildableReference
                BuildableIdentifier = "primary"
                BlueprintIdentifier = "XXMessengerClientTests"