fix!: Allow async functions without send on async trait

[phated]

Related issue(s)

Resolves (link to issue)

Description

Summary of changes

This allows implementors of #[async_trait] to not mark their functions as Send. This is needed because the browser fetch API is async but not Send.

Dependency additions / changes

(If applicable.)

Test additions / changes

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Checklist

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt with default settings.
• I have linked this PR to the issue(s) that it resolves.
• I have reviewed the changes on GitHub, line by line.
• I have ensured all changes are covered in the description.

Additional context

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