refactoring(http, headers): headers mdw refactoring

[rustatian]

Reason for This PR

• refactoring

Description of Changes

• Update configuration usage.
• Update plugin's Init.

License Acceptance

By submitting this pull request, I confirm that my contribution is made under the terms of the MIT license.

PR Checklist

[Author TODO: Meet these criteria.] [Reviewer TODO: Verify that these criteria are met. Request changes if not]

• [x] All commits in this PR are signed (git commit -s).
• [x] The reason for this PR is clearly provided (issue no. or explanation).
• [x] The description of changes is clear and encompassing.
• [x] Any required documentation changes (code and docs) are included in this PR.
• [x] Any user-facing changes are mentioned in CHANGELOG.md.
• [x] All added/changed functionality is tested.

[codecov[bot]]

Codecov Report

Merging #135 (ac2acde) into master (1052d92) will increase coverage by 0.09%. The diff coverage is 86.20%.

@@            Coverage Diff             @@
##           master     #135      +/-   ##
==========================================
+ Coverage   65.20%   65.29%   +0.09%     
==========================================
  Files         138      138              
  Lines       11007    11008       +1     
==========================================
+ Hits         7177     7188      +11     
+ Misses       3104     3097       -7     
+ Partials      726      723       -3     

Impacted Files	Coverage Δ
http/middleware/headers/plugin.go	86.66% <86.20%> (+0.18%)	:arrow_up:
sqs/sqsjobs/item.go	65.78% <0.00%> (-1.32%)	:arrow_down:
redis/pubsub/pubsub.go	72.86% <0.00%> (+2.32%)	:arrow_up:
beanstalk/beanstalkjobs/item.go	80.00% <0.00%> (+2.85%)	:arrow_up:
websockets/executor/executor.go	68.18% <0.00%> (+5.30%)	:arrow_up:

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