Test Amplify Schema

1.schema.graphql

type User @model {
  id: String! # Cognito username
  uuid: String! # Cognito UUID
  displayName: String
  profileImage: AWSURL

  journals: [Journal] @connection(name: "UserJournals", sortField: "createdAt") # HAS MANY JOURNALS
  comments: [Comment] @connection(name: "UserComments", sortField: "createdAt") # HAS MANY COMMENTS
  lovedJournals: [UserLovedJournal] @connection(name: "UserLovedJournals")  # HAS MANY LOVED JOURNALS
  lovedComments: [UserLovedComment] @connection(name: "UserLovedComments")  # HAS MANY LOVED COMMENTS
  notifications: [Notification] @connection(name: "UserNotifications", sortField: "createdAt") # HAS MANY NOTIFICATIONS
  following: [Following] @connection(name: "UserFollowings", sortField: "createdAt") # HAS MANY FOLLOWINGS
  follower: [Follower] @connection(name: "UserFollowers", sortField: "createdAt") # HAS MANY FOLLOWERS

  createdAt: AWSDateTime
  updatedAt: AWSDateTime
}

type Following @model(queries: null) {
  id: ID!
  user: User! @connection(name: "UserFollowings")
  following: User!

  createdAt: AWSDateTime
}

type Follower @model(queries: null) {
  id: ID!
  user: User! @connection(name: "UserFollowers")
  follwer: User!
  
  createdAt: AWSDateTime
}

type UserLovedJournal @model(queries: null) {
  id: ID!
  journal: Journal @connection(name: "JournalLovedUsers")
  user: User @connection(name: "UserLovedJournals")

  createdAt: AWSDateTime
}

type Journal 
  @model
  @key(name: "privacy", fields: ["privacy", "createdAt"], queryField: "listPublicJournals")
  @auth(
    rules: [
      { allow: owner },
      { allow: groups, groups: ["Admin"] }
    ]
  ) {
  id: ID!
  privacy: String! # PRIVATE or PUBLIC
  draft: Boolean!
  content: String!

  author: User @connection(name: "UserJournals")  # BELONGS TO WHICH AUTHOR
  lovedUsers: [UserLovedJournal] @connection(name: "JournalLovedUsers") # HAS MANY LOVED USERS
  comments: [Comment] @connection(name: "JournalComments", sortField: "createdAt")  # HAS MANY COMMENTS

  createdAt: AWSDateTime
  updatedAt: AWSDateTime
}

type UserLovedComment @model(queries: null) {
  id: ID!
  comment: Comment @connection(name: "CommentLovedUsers")
  user: User @connection(name: "UserLovedComments")
  
  createdAt: AWSDateTime
}

type Comment @model {
  id: ID!
  content: String!

  author: User @connection(name: "UserComments")  # BELONGS TO WHICH AUTHOR
  journal: Journal @connection(name: "JournalComments") # BELONGS TO WHICH JOURNAL
  lovedUsers: [UserLovedComment] @connection(name: "CommentLovedUsers") # HAS MANY LOVED USERS

  createdAt: AWSDateTime
  updatedAt: AWSDateTime
}

type Notification 
  @model
  @auth(
    rules: [
      { allow: owner },
      { allow: groups, groups: ["Admin"] }
    ]
  ) {
  id: ID!
  content: String!
  category: String!
  link: String!
  read: Boolean!

  user: User! @connection(name: "UserNotifications")

  createdAt: AWSDateTime
}

#https://aws-amplify.github.io/docs/cli-toolchain/graphql#add-a-custom-resolver-that-targets-a-dynamodb-table-from-model
#https://aws-amplify.github.io/docs/cli-toolchain/graphql#add-a-custom-resolver-that-targets-an-aws-lambda-function
# type Query {
#   getPublicJournalList(limit: Int, nextToken: String): [Journal] @function(name: "gnjamplifyGetPublicJournalList-${env}")
# }

type publicJournalsConnection {
  items: [Journal]
  nextToken: String
}

type Query {
  getPublicJournals(privacy: String!, limit: Int, nextToken: String, sortDirection: DirectionEnum): publicJournalsConnection
  getPublicJournalEntry(id: String!): Journal
}

enum DirectionEnum {
  ASC
  DESC
}

2.sample-input.graphql

mutation CreateUser {
  createUser(
    input: {
      id: "koingdev"
      displayName: "SSK"
      uuid: "cognito-uuid0001"
    }
  ) {
    id
  }
}

mutation CreateJournal {
  createJournal(
    input: {
      id: "journal-0001"
      journalAuthorId: "koingdev"
      privacy: PRIVATE
      draft: false
      content: "{ \"value\" : \"My first journal\" }"
    }
  ) {
    id
    content
  }
}

mutation CreateComment {
  createComment(
    input: {
      id: "cmt-0001"
      commentAuthorId: "koingdev"
      commentJournalId: "journal-0001"
      content: "How are you ?" 
    }
  ) {
    id
    content
  }
}

mutation UserLoveJournal {
  createUserLovedJournal(
    input: {
      userLovedJournalUserId: "koingdev"
      userLovedJournalJournalId: "journal-0001"
    }
  ) {
    id
  }
}

mutation UserLoveComment {
  createUserLovedComment(
    input: {
      userLovedCommentUserId: "koingdev"
      userLovedCommentCommentId: "cmt-0001"
    }
  ) {
    id
  }
}

query GetUserInfo {
  getUser(id: "koingdev") {
    id
    uuid
    journals {
      items {
        id
        privacy
        content
        comments {
          items {
            id
            content
          }
        }
      }
    }
    lovedJournals {
      items {
        journal {
          id
          content
        }
      }
    }
    lovedComments {
      items {
        comment {
          id
          content
        }
      }
    }
  }
}

3.sample-output.json

{
  "data": {
    "getUser": {
      "id": "koingdev",
      "uuid": "cognito-uuid0001",
      "journals": {
        "items": [
          {
            "id": "journal-0001",
            "privacy": "PRIVATE",
            "content": "{\"value\":\"My first journal\"}",
            "createdAt": "2019-08-01T17:10:53.911Z",
            "comments": {
              "items": [
                {
                  "id": "cmt-0001",
                  "content": "How are you ?"
                }
              ]
            }
          },
          {
            "id": "journal-0002",
            "privacy": "PRIVATE",
            "content": "{\"value\":\"My 2nd journal\"}",
            "createdAt": "2019-08-01T17:11:31.578Z",
            "comments": {
              "items": []
            }
          },
          {
            "id": "journal-0005",
            "privacy": "PRIVATE",
            "content": "{\"value\":\"Computer is magic\"}",
            "createdAt": "2019-08-01T17:43:30.917Z",
            "comments": {
              "items": []
            }
          },
          {
            "id": "journal-0003",
            "privacy": "PRIVATE",
            "content": "{\"value\":\"I am good\"}",
            "createdAt": "2019-08-01T17:43:46.874Z",
            "comments": {
              "items": []
            }
          }
        ]
      },
      "lovedJournals": {
        "items": [
          {
            "journal": {
              "id": "journal-0001",
              "content": "{\"value\":\"My first journal\"}"
            }
          }
        ]
      },
      "lovedComments": {
        "items": [
          {
            "comment": {
              "id": "cmt-0001",
              "content": "How are you ?"
            }
          }
        ]
      }
    }
  }
}

Added Notification here. Want to make sure this makes sense.
LGTM ^^

@auth is needed or not? as you can see from above GraphQL, I added
I think that it is better to put @auth rule base on your requirement.