fix #7599 chore(nimbus): explicitly convert snake to camel case

[jaredlockhart]

Because

• snake_case is idiomatic for Python
• camelCase is idiomatic for javascript/typescript
• The graphql library graphene automatically converts snake_case to camelCase
• After we remove graphene, we want to keep the frontend interface the same to not have to modify the entire frontend
• We need to disable the automatic snake/camel case conversion and explicitly handle it in the serializers

This commit

• Disables the automatic snake/camel case conversion
• Updates all the graphene/serializer layers to explicitly map snake_case fields to their camelCase counterparts while keeping the frontend interface unmodified