New example of higher-ranked lifetime error

[nappa85]

As discussed in #92096, I've found another example of higher-ranked lifetime error

Long story short, I was developing a struct that contains a string key and a database connection. For other problems the connection was already owned, but the key was a Cow<'key, str> to avoid allocation when unneeded.
The constructor accepted S: Into<Cow<'key, str>>, so you can pass in even a static str or a String, no problems.

Everything was looking good, mi lib crates using that struct built fine, until I plugged it into my warp webserver, at this point I've got my higher-ranked lifetime error.
You can test yourself in this project where I've replicated the problem: https://github.com/nappa85/hrtb-error

To solve the problem, I've converted the Cow<'key, str> into a String and removed the lifetime from my struct.
To test the solution you simply have to change the pointed branch from "cow" to "owned" inside Cargo.toml

[eholk]

Discussed in wg-async triage meeting today.

Thanks for the helpful repo that demonstrates the issue! A good next step would be to see if we can reduce the issue even further.