add gratitude and request status to scehma

[utunga]

After issue #49 we can add some things to the schema

Suggestion:

type User {
    id: ID!
    email: String! @id
    name: String!
    age: Int
  	isAdmin: Boolean
  	createdTimestamp: DateTime
    requests: [Request] @hasInverse(field: "owner")
  	skills: [Skill] @hasInverse(field: "owner")
	  gratitudeSent: [Gratitude] @hasInverse(field: "from")
	  gratitudeReceived: [Gratitude] @hasInverse(field: "to")
}

type Request {
    id: ID!
    owner: User! @hasInverse(field: "requests")
    title: String! @search
    message: String! @search
  	status: RequestStatus!
  	hashtagVariants: [HashtagVariant]! @hasInverse(field: "requests")
  	createdTimestamp: DateTime
}

enum RequestStatus {
  	OPEN,
	  TENTATIVE,
	  FILLED,
	  DONE
}

type Skill {
  	id: ID!
  	owner: User! @hasInverse(field: "skills")
    title: String
    message: String
    hashtagVariants: [HashtagVariant]! @hasInverse(field: "skills")
    isAvailable: Boolean
  	createdTimestamp: DateTime
}

type Gratitude {
  	id: ID!
  	from: User! @hasInverse(field: "gratitudeSent")
  	to: User! @hasInverse(field: "gratitudeReceived")
        message: String
        hashtagVariants: [HashtagVariant]! @hasInverse(field: "skills")
  	createdTimestamp: DateTime
}
``