Some types missing default values for @odata.type

[andrueastman]

Additionally, after some more thinking, could we also take that opportunity to set a default value for the odata.type property to the actual odata type? i.e. #microsoft.graph.entity.
This would enable kiota to initialize this property at runtime and send it to the service.

Originally posted by @baywet in #243 (comment)

[andrueastman]

Taking a look at the latest generation the FileAttachment schema is missing the deafult value for @odata.type

    microsoft.graph.fileAttachment:
      allOf:
        - $ref: '#/components/schemas/microsoft.graph.attachment'
        - title: fileAttachment
          type: object
          properties:
            contentBytes:
              type: string
              description: The base64-encoded contents of the file.
              format: base64url
              nullable: true
            contentId:
              type: string
              description: The ID of the attachment in the Exchange store.
              nullable: true
            contentLocation:
              type: string
              description: Do not use this property as it is not supported.
              nullable: true
      x-ms-discriminator-value: '#microsoft.graph.fileAttachment'

Its base type Attachment however has the default value defined as '#microsoft.graph.attachment'

    microsoft.graph.attachment:
      allOf:
        - $ref: '#/components/schemas/microsoft.graph.entity'
        - title: attachment
          required:
            - '@odata.type'
          type: object
          properties:
            contentType:
              type: string
              description: The MIME type.
              nullable: true
            isInline:
              type: boolean
              description: 'true if the attachment is an inline attachment; otherwise, false.'
            lastModifiedDateTime:
              pattern: '^[0-9]{4,}-(0[1-9]|1[012])-(0[1-9]|[12][0-9]|3[01])T([01][0-9]|2[0-3]):[0-5][0-9]:[0-5][0-9]([.][0-9]{1,12})?(Z|[+-][0-9][0-9]:[0-9][0-9])$'
              type: string
              description: 'The Timestamp type represents date and time information using ISO 8601 format and is always in UTC time. For example, midnight UTC on Jan 1, 2014 is 2014-01-01T00:00:00Z'
              format: date-time
              nullable: true
            name:
              type: string
              description: The display name of the attachment. This does not need to be the actual file name.
              nullable: true
            size:
              maximum: 2147483647
              minimum: -2147483648
              type: integer
              description: The length of the attachment in bytes.
              format: int32
            '@odata.type':
              type: string
              default: '#microsoft.graph.attachment'

The adding of the default value seems to apply only if the schema has a discriminator defined. We would probably need this defined in the derived schema as well so that Kiota can initialize the property for type disambiguation in the API.

[baywet]

same problem with user for example