Use json_schema for summary generation

[yujonglee]

    schema = %{
      type: "object",
      properties: %{
        keywords: %{
          type: "array",
          description: "List of extracted keywords. Upto 20 keywords are allowed",
          items: %{
            type: "object",
            description:
              "Extracted keyword. Keyword must be domain specific, or frequently used words in the document. If the document is defining new terms, that must be extracted.",
            properties: %{
              value: %{
                type: "string",
                description: "Keyword itself(one or two words)"
              },
              description: %{
                type: "string",
                description: "Short description of the keyword"
              }
            },
            required: ["value", "description"]
          }
        }
      },
      required: ["keywords"]
    }

The blocker is Azure version. (we need 2024-08-06)