fix: invalid numerics notation in session data

[nekiro]

This PR fixes invalid numerics notation in stored session data.

Checklist

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• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
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• I have added tests that prove my fix is effective or that my feature
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Further Comments

Hydra (as of not sure which version, it worked fine on 1.8.5 though) incorrectly converts big (larger than 999999) numeric values into exponential notation.
This breaks the compatibility with older hydra versions and is in fact incorrect.

Playground to test this change:
https://go.dev/play/p/NDYofwinU4M

Reference:
https://groups.google.com/g/golang-nuts/c/Fd5jUfHxbh8

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.23%. Comparing base (50301e0) to head (d6e4b57).
Report is 9 commits behind head on master.

❗ Current head d6e4b57 differs from pull request most recent head f992e81. Consider uploading reports for the commit f992e81 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3722      +/-   ##
==========================================
- Coverage   76.39%   76.23%   -0.17%     
==========================================
  Files         135      134       -1     
  Lines       10283    10211      -72     
==========================================
- Hits         7856     7784      -72     
- Misses       1907     1910       +3     
+ Partials      520      517       -3     

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[aeneasr]

This will only fix it for this specific endpoint. Another way of solving this is to override MarshalJSON of flow.AcceptOAuth2ConsentRequest and similar methods.

[nekiro]

I don't think other "endpoints" have problems, this issue is specifically with the data saved into session. I didn't notice other places where this would be an issue.

[nekiro]

Hey, I added small helper and replaced occurrences of decode in several handlers. I'm not sure how can I use MarshalJSON methods with this change as there is only call to json.Marshal there.
I'm also not really a go developer, so I'm not used to work with this language.