Convert pagination ISE into a Bad Request response

Errors in parsing the pagination query string parameters can be returned
to the client and do not need to propagate up to the logging middleware.

The following have been observed in production logs:

* error="cannot parse integer from empty string" for
  `/api/v1/crates?page=&per_page=50&sort=downloads`
* error="invalid digit found in string" for
  `/api/v1/crates?page=1&per_page=100%22%EF%BC%8Cexception"`

Author: jtgeibel

src/controllers/helpers/pagination.rs

@@ -16,7 +16,7 @@ pub(crate) enum Page {
 impl Page {
     fn new(params: &IndexMap<String, String>) -> AppResult<Self> {
         if let Some(s) = params.get("page") {
-            let numeric_page = s.parse()?;
+            let numeric_page = s.parse().map_err(|e| bad_request(&e))?;
             if numeric_page < 1 {
                 return Err(cargo_err(&format_args!(
                     "page indexing starts from 1, page {} is invalid",
@@ -44,7 +44,7 @@ impl PaginationOptions {
 
         let per_page = params
             .get("per_page")
-            .map(|s| s.parse())
+            .map(|s| s.parse().map_err(|e| bad_request(&e)))
             .unwrap_or(Ok(DEFAULT_PER_PAGE))?;
 
         if per_page > MAX_PER_PAGE {