Print unconfigured Data<T> type when attempting extraction

[cquintana-verbio]

PR Type

Other

PR Checklist

Check your PR fulfills the following:

• A changelog entry has been made for the appropriate packages.
• Format code with the latest stable rustfmt

Overview

This PR aims to help developers when facing the

Failed to construct App-level Data extractor. Request path: "/your-endpoint"

Now, it will print something like the following:

Failed to construct App-level Data extractor. Request path: "/your-endpoint" (type = THE_TYPE_WILL_APPEAR_HERE)

[robjtede]

Great find! I didnt know about that. This will be a significant improvement to DX.

[codecov-io]

Codecov Report

Merging #1743 into master will increase coverage by 0.00%.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master    #1743   +/-   ##
=======================================
  Coverage   53.60%   53.60%           
=======================================
  Files         128      126    -2     
  Lines       11997    11996    -1     
=======================================
  Hits         6431     6431           
+ Misses       5566     5565    -1     

Impacted Files	Coverage Δ
src/data.rs	93.51% <0.00%> (-0.88%)	⬇️
actix-http/src/header/common/last_modified.rs
actix-http/src/header/common/accept_language.rs
actix-http/src/header/common/accept_charset.rs
actix-http/src/header/common/content_language.rs	0.00% <0.00%> (ø)

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