Multiple belongsTo associations in same model to same target not working with inverse

[apstanisic]

Issue Creation Checklist

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Bug Description

When using multiple belongsTo associations in same model to same target with inverse, it complains that associations are not compatible.
Associations are defined from side where FK is located, with inverse property specified.
First associations is normally defined. But second is causing problem. Second associations works if inverse is removed.
I think that the problem is when defining second relation with inverse, it is not creating inverse relation properly, since it's comparing it with already existing 1st relation

Reproducible Example

Here is the link to the SSCCE for this issue: link
PR: link

 class Post extends Model {}
  class Author extends Model {}

  Post.init(
    {
      id: { type: DataTypes.INTEGER, primaryKey: true, autoIncrement: true },
      content: DataTypes.TEXT,
      authorId: DataTypes.INTEGER,
      coAuthorId: DataTypes.INTEGER,
    },
    {
      sequelize,
      modelName: "Post",
    }
  );

  Author.init(
    {
      id: { type: DataTypes.INTEGER, primaryKey: true, autoIncrement: true },
      name: DataTypes.TEXT,
    },
    {
      sequelize,
      modelName: "Author",
    }
  );

  Post.belongsTo(Author, {
    foreignKey: "authorId",
    as: "author",
    targetKey: "id",
    inverse: { as: "myBooks", type: "hasMany" },
  });

  Post.belongsTo(Author, {
    foreignKey: "coAuthorId",
    as: "coAuthor",
    targetKey: "id",
  // Code works if this line is removed
    inverse: { as: "notMyBooks", type: "hasMany" },
  });

What do you expect to happen?

To define 2 associations with inverse associations.

What is actually happening?

It throws an error saying that they are incompatible because their options are not reconcilable.
Error:

    [cause]: AssociationError [SequelizeAssociationError]: The association "notMyBooks" needs to define the BelongsTo association "Author" from Post to Author,
    but that child association has already been defined as BelongsTo, to Author by this call:
    
    Post.belongsTo(Author, {
      foreignKey: { name: 'authorId' },
      as: 'author',
      targetKey: 'id',
      inverse: { as: 'myBooks', type: 'hasMany' },
      hooks: false,
      name: { plural: 'authors', singular: 'author' }
    })
    
    That association would be re-used if compatible, but it is incompatible because their options are not reconcilable:
    
    Options of the association to create:
    {
      as: 'Author',
      foreignKey: { name: 'coAuthorId' },
      hooks: false,
      name: { plural: 'Authors', singular: 'Author' },
      targetKey: 'id'
    }
    
    Options of the existing association:
    {
      as: 'Author',
      foreignKey: { name: 'authorId' },
      hooks: false,
      name: { plural: 'Authors', singular: 'Author' },
      targetKey: 'id'
    }

Environment

• Sequelize version: 7.0.0-alpha.20
• Node.js version: v18.13.0
• If TypeScript related: TypeScript version: 4.9.4, Not TS related
• Database & Version: postgres 15 and sqlite from sscce
• Connector library & Version: pg 8.9.0 in project, and default sqlite from sscce

Would you be willing to resolve this issue by submitting a Pull Request?

Open to take a look, but I think this is too deep in the library.

• Yes, I have the time and I know how to start.
• Yes, I have the time but I will need guidance.
• No, I don't have the time, but my company or I are supporting Sequelize through donations on OpenCollective.
• No, I don't have the time, and I understand that I will need to wait until someone from the community or maintainers is interested in resolving my issue.

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[ephys]

Definitely sounds like a bug.
All associations are built on top of belongsTo (it's the association that actually handles the Foreign Key), but the inverse hasMany association should not be trying to re-create the belongsTo association - it already exists

As a temporary workaround, you should be able to define your association (+ inverse) using hasMany instead of belongsTo

PS: thank you for trying out Sequelize 7 😄