Add useful body text to error responses from /database/publish route

[gefjon]

At some point (probably introducing cloud-next), we merged a regression in the HTTP API's error reporting, where now any errors in /database/publish will return a 500 with no body text. The CLI uses the response body text to print its error, so we get such gems as:

info: component 'rust-std' for target 'wasm32-unknown-unknown' is up to date
   Compiling bitcraft-spacetimedb v0.1.0 (C:\ClockworkLabs\BitCraft\packages\game)
    Finished release [optimized] target(s) in 1m 02s
checking crate with spacetimedb's clippy configuration
   Compiling bitcraft-spacetimedb v0.1.0 (C:\ClockworkLabs\BitCraft\packages\game)
    Finished dev [unoptimized + debuginfo] target(s) in 19.43s
Error:

I also notice that we return BAD_REQUEST for invalid credentials, rather than UNAUTHORIZED.

For at least the /database/publish route, and ideally the entire HTTP API surface:

• Replace auth_or_bad_request with auth_or_unauth.
• Replace log_and_500 with specific error response tuples of (STATUS_CODE, "Message"), where STATUS_CODE is an appropriate HTTP error code, and "Message" is a string describing what went wrong. The CLI will show that string to users on failure.

[kim]

Is this just due to bad merges?

[gefjon]

Closed by Kim's linked PR and #338 .