Unintentional breaking change, removing #[async_trait], in patch release

[eopb]

Version 7.0.2 introduced a breaking change, replacing #[async_trait] on public traits with async functions in traits #1468.

This has resulted in breakage for others, not just myself:

• Use impl Future instead of async-trait in most traits. #1468 (comment)
• Use impl Future instead of async-trait in most traits. #1468 (comment)

Ideally 7.0.2 should be yanked and #1468 reverted. #1468 should only be included in 8.0.0.

[noehoro]

We have faced the same issue.

[ckruse]

I face the issue that I now hit this error

overflow evaluating the requirement `&str: Sync`

when merging too many objects. I have to increase the recursion limit to 512 to get it working again