Through model casing has a different name depending on eager or lazy loading

[ephys]

Issue Creation Checklist

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Bug Description

If you have a BelongsToMany association, and you load that association, the data of the through model will be placed on a different key depending on whether it was eager loaded or lazy loaded

When eager loaded, the key is the name of the model

When lazy loaded, the key is the name of one of the associations

To replicate the v6 behavior, the key should always be the name of the model

Reproducible Example

Here is the link to the SSCCE for this issue: sequelize/sequelize-sscce#275

Environment

• Sequelize version: 7.0.0-alpha.36
• Node.js version: v18.16.0
• If TypeScript related: TypeScript version: N/A
• Database & Version: Reproduced on sqlite, postgres 14
• Connector library & Version: pg 8.11.3

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

• 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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[shraf]

i want to work on this issue, is there an opened branch to work on or should i fork & create a new PR? @ephys