Prefabs | Introduce sanitation of prefab doms on loading (#1929)

* Update PrefabLoader to sanitize ingested prefabs and have core systems operate with default values

Signed-off-by: sconel <sconel@amazon.com>
Signed-off-by: Danilo Aimini <82231674+AMZN-daimini@users.noreply.github.com>

* Remove IsExplicitDefault implementation to avoid confusion (since the function isn't virtual).
Avoid copying PrefabDoms over in SanitizeLoadTemplate.

Signed-off-by: Danilo Aimini <82231674+AMZN-daimini@users.noreply.github.com>

* Address naming and commenting concerns from PR reviews.

Signed-off-by: Danilo Aimini <82231674+AMZN-daimini@users.noreply.github.com>

* Fix to error detection code

Signed-off-by: Danilo Aimini <82231674+AMZN-daimini@users.noreply.github.com>

* Add support for all uuid formats for zero check.

Signed-off-by: Danilo Aimini <82231674+AMZN-daimini@users.noreply.github.com>

Co-authored-by: sconel <sconel@amazon.com>

Code/Framework/AzCore/AzCore/Math/UuidSerializer.cpp

@@ -23,6 +23,8 @@ namespace AZ
     }
 
     JsonUuidSerializer::JsonUuidSerializer()
+        : m_zeroUuidString(AZ::Uuid::CreateNull().ToString<AZStd::string>())
+        , m_zeroUuidStringNoDashes(AZ::Uuid::CreateNull().ToString<AZStd::string>(true, false))
     {
         m_uuidFormat = AZStd::regex(R"(\{[a-f0-9]{8}-?[a-f0-9]{4}-?[a-f0-9]{4}-?[a-f0-9]{4}-?[a-f0-9]{12}\})",
             AZStd::regex_constants::icase | AZStd::regex_constants::optimize);
@@ -53,7 +55,7 @@ namespace AZ
 
         Uuid* valAsUuid = reinterpret_cast<Uuid*>(outputValue);
 
-        if (IsExplicitDefault(inputValue))
+        if (IsExplicitDefault(inputValue) || (inputValue == m_zeroUuidString.c_str()) || (inputValue == m_zeroUuidStringNoDashes.c_str()))
         {
             *valAsUuid = AZ::Uuid::CreateNull();
             return MessageResult("Uuid value set to default of null.", JSR::ResultCode(JSR::Tasks::ReadField, JSR::Outcomes::DefaultsUsed));

Code/Framework/AzCore/AzCore/Math/UuidSerializer.h

@@ -47,6 +47,8 @@ namespace AZ
             const Uuid& valueTypeId, JsonSerializerContext& context);
 
     private:
+        const AZStd::string m_zeroUuidString;
+        const AZStd::string m_zeroUuidStringNoDashes;
         AZStd::regex m_uuidFormat;
     };
 } // namespace AZ