search: check for null bytes before querying

[LawnGnome]

PostgreSQL has an unusual definition of UTF8 that doesn't allow for null bytes, even though they are technically valid UTF-8 by any other definition (including Rust's str type). Sending a crate search request that includes a null byte will eventually result in a database error anyway, but let's save Sentry the trouble and just 400 out early.

I did a quick audit of other places that we use query parameters and don't see any other code paths where we use a string directly as a query parameter, but I won't pretend this was a super detailed survey. (Fun fact: I can actually see the power usage for my laptop increase on my fancy new charger when I hit "show references" on the query method in RequestUtils.)

Fixes #9444.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.10%. Comparing base (2baaf0b) to head (110e569).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9473      +/-   ##
==========================================
+ Coverage   89.09%   89.10%   +0.01%     
==========================================
  Files         286      286              
  Lines       29035    29039       +4     
==========================================
+ Hits        25868    25875       +7     
+ Misses       3167     3164       -3     

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[eth3lbert]

Is it okay to simply write it as:

Suggested change

	let option_param = |s| match params.get(s).map(|v| v.as_str()) {
	Some(v) if v.contains('\0') => Err(bad_request(format!(
	"parameter {s} cannot contain a null byte"
	))),
	Some(v) => Ok(Some(v)),
	None => Ok(None),
	};
	let option_param = |s| match params.get(s).map(|v| v.as_str()) {
	Some(v) if v.contains('\0') => Err(bad_request(format!(
	"parameter {s} cannot contain a null byte"
	))),
	v @ _ => Ok(v), // or just v => Ok(v)
	};

Or will it be more difficult to read in this way?