Add SPNEGO authentication header

[TheLydonKing]

Added WWW-Authentication: Negotiate Header to 401 Status response when Kerberos is enabled

closes #106

[github-actions]

JaCoCo code coverage report - scala:2.12.17

File	Coverage [84.42%]	🍏
SecurityConfig.scala	84.91%	🍏
TokenController.scala	84.12%	🍏

Total Project Coverage	62.72%	🍏

[dk1844]

There is also the matter of existing Swagger v3 OAS Annotations (aka OpenAPI docs) - this has bears no information about the Negotiate Auth option.
GET http://localhost:9090/v3/api-docs.yaml gives

  /token/generate:
    post:
      security:
      - basicAuth: []
  ...
  securitySchemes:
    basicAuth:
      type: http
      scheme: basic
...

but it should probably give

  /token/generate:
    post:
      security:
      - negotiate: []
      - basicAuth: []
  ...
  securitySchemes:
    negotiate:
      type: http
      scheme: negotiate
    basicAuth:
      type: http
      scheme: basic

I think that the solution might be adding another

  @SecurityRequirement(name = "negotiate")

and introducing something like

@SecurityScheme(
  name = "negotiate",
  `type` = SecuritySchemeType.HTTP,
  scheme = "negotiate"
)

I am not sure that it is entirely correct (perhaps do your own research how it should be done properly, but something along these lines

[dk1844]

LGTM (tested on my machine)