fix: add handlers in correct order to handle CORS requests properly

[marcinfigiel]

Fix the order in which handlers are added to the Negroni stack so the DecisionHandler is last and doesn't intercept CORS preflight requests.

Related issue(s)

#1054

Checklist

• I have read the contributing guidelines.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security vulnerability, I
  confirm that I got the approval (please contact
  security@ory.sh) from the maintainers to push
  the changes.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added or changed the documentation.

Further Comments

[codecov]

Codecov Report

Merging #1055 (3cc1552) into master (7e7d45e) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 3cc1552 differs from pull request most recent head 37dd8d4. Consider uploading reports for the commit 37dd8d4 to get more accurate results

@@           Coverage Diff           @@
##           master    #1055   +/-   ##
=======================================
  Coverage   77.79%   77.79%           
=======================================
  Files          81       80    -1     
  Lines        3967     3949   -18     
=======================================
- Hits         3086     3072   -14     
+ Misses        600      598    -2     
+ Partials      281      279    -2     

Impacted Files	Coverage Δ
cmd/server/server.go	76.50% <100.00%> (ø)
...peline/authn/authenticator_oauth2_introspection.go	80.00% <100.00%> (-0.22%)	⬇️

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[vinckr]

Hello @marcinfigiel
Congrats on merging your first PR in Ory 🎉 !
Your contribution will soon be helping secure millions of identities around the globe 🌏.
As a small token of appreciation we send our first time contributors a gift package to welcome them to the community.
Please drop me an email and I will forward you the form to claim your Ory swag!