feat: hosting GraphQL server

[boscohyun]

• Introduce Lib9c.GraphQL project with some types: PlanetNameType, SheetNameType, SheetType for SheetObject.
• Configure GraphQL service to Mimir project with some queries: sheetNames, sheet
• Run project and connect to {host:port}/graphql.

# schema definition
"""
The name of the planet.
See https://planets.nine-chronicles.com/planets/ or https://planets-internal.nine-chronicles.com/planets/ for more information.
"""
enum PlanetName {
  """
  The name of the planet odin.
  """
  ODIN

  """
  The name of the planet heimdall.
  """
  HEIMDALL
}

scalar SheetNameType

type SheetObject {
  """
  The name of the sheet.
  """
  name: SheetNameType!

  """
  The CSV content of the sheet.
  """
  csv: String

  """
  The JSON content of the sheet.
  """
  json: String
}

type Query {
  sheetNames(planetName: PlanetName!): [String!]!
  sheet(planetName: PlanetName!, sheetName: SheetNameType!): SheetObject!
}

[ipdae]

There is a reason you created a separate class to implement it?

[boscohyun]

In Mimir's existing API, users could get a sheet in either CSV or JSON when they requested it. To adapt this to GraphQL, I defined a separate object.
Later on, I also expected this SheetObject to have a sheet address of type Address added to it.

미미르에서 기존에 제공하던 API에서는 사용자가 시트를 조회할 때, CSV나 JSON 중 원하는 형태로 받을 수 있었습니다. 이를 GraphQL에 적용하기 위해서 별도의 오브젝트를 정의했습니다.
이후에는 이 SheetObject에 Address 타입의 시트 주소가 추가되는 걸 기대하기도 했습니다.