feat(AI Chat): Add authoring config param for whether chat gpt is enabled

[geoffreykwan]

Changes

• Added chatGptEnabled param to authoring config

Test

• Test with feat(AI Chat): Check if chat gpt is enabled when adding items WISE-Client#1732
• If OPENAI_API_KEY is
  • not in application.properties, chatGptEnabled should be false
  • in application.properties but is empty, chatGptEnabled should be false
  • is set to a string in application.properties, chatGptEnabled should be true

[hirokiterashima]

LGTM