chore: fix clippy warnings

[duncanpharvey]

What does this PR do?

Fixes clippy warnings.

Motivation

https://github.com/DataDog/serverless-components/actions/runs/29588791501/job/87912458431?pr=146

error: redundant reference in `format!` argument
  --> crates/dogstatsd/src/datadog/shipping.rs:46:47
   |
46 |         let url = format!("{}/api/v2/series", &self.metrics_intake_url_prefix);
   |                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove the redundant `&`: `self.metrics_intake_url_prefix`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.97.0/index.html#useless_borrows_in_formatting
   = note: `-D clippy::useless-borrows-in-formatting` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::useless_borrows_in_formatting)]`

error: redundant reference in `format!` argument
  --> crates/dogstatsd/src/datadog/shipping.rs:57:51
   |
57 |         let url = format!("{}/api/beta/sketches", &self.metrics_intake_url_prefix);
   |                                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove the redundant `&`: `self.metrics_intake_url_prefix`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.97.0/index.html#useless_borrows_in_formatting

error: this block may be rewritten with the `?` operator
  --> crates/dogstatsd/src/util.rs:43:5
   |
43 | /     if let Some(first_char) = chars.next() {
44 | |         if !first_char.is_ascii_alphabetic() {
45 | |             tracing::error!(
46 | |                 "DD_STATSD_METRIC_NAMESPACE must start with a letter, got: '{}'. Ignoring namespace.",
...  |
52 | |         return None;
53 | |     }
   | |_____^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.97.0/index.html#question_mark
   = note: `-D clippy::question-mark` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::question_mark)]`
help: replace it with
   |
43 ~     {
44 +         let first_char = chars.next()?;
45 +         if !first_char.is_ascii_alphabetic() {
46 +             tracing::error!(
47 +                 "DD_STATSD_METRIC_NAMESPACE must start with a letter, got: '{}'. Ignoring namespace.",
48 +                 trimmed
49 +             );
50 +             return None;
51 +         }
52 +     }
   |

Additional Notes

Describe how to test/QA your changes

[Copilot]

Pull request overview

This PR addresses Rust Clippy warnings in the DogStatsD crate, keeping CI green under -D warnings while preserving existing behavior.

Changes:

• Simplified parse_metric_namespace control flow by using the ? operator for early-return on missing first character.
• Removed redundant borrows in format! calls when constructing Datadog intake URLs.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
crates/dogstatsd/src/util.rs	Refactors namespace parsing to use ? for Option early-return and satisfy Clippy.
crates/dogstatsd/src/datadog/shipping.rs	Cleans up format! argument borrowing to satisfy Clippy.

Comments suppressed due to low confidence (1)

crates/dogstatsd/src/datadog/shipping.rs:50

• trace!("Sending body: {:?}", series) logs the full metrics payload. Metric tags/names can contain customer identifiers; logging the full payload risks leaking sensitive data and can be very noisy. Prefer logging only counts/sizes.

        let safe_body = serde_json::to_vec(&series)
            .map_err(|e| ShippingError::Payload(format!("Failed to serialize series: {e}")))?;
        trace!("Sending body: {:?}", &series);
        self.ship_data(url, safe_body, "application/json").await