fix: upgrade guide 0.5->0.8

[vinckr]

As suggested in
#2104
this

• updates UPGRADE.md with some highlevel information on the breaking changes and links to the respective sections in the CHANGELOG for quick reference
• adds a document upgrade.md in the /docs under "Debug & Help".
  I thought it makes more sense there, since it is not a very common occurance and the guide is not very extensive (yet).

I had trouble recreating a proper upgrade scenario to test everything using the quickstart or my own deployment, so I am hoping from some input.

Related issue(s)

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 green light (please contact
  [email protected]) 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 #2132 (0f4df7a) into master (b9fc641) will increase coverage by 0.01%.
The diff coverage is n/a.

❗ Current head 0f4df7a differs from pull request most recent head 366e671. Consider uploading reports for the commit 366e671 to get more accurate results

@@            Coverage Diff             @@
##           master    #2132      +/-   ##
==========================================
+ Coverage   75.21%   75.23%   +0.01%     
==========================================
  Files         293      293              
  Lines       15609    15600       -9     
==========================================
- Hits        11741    11736       -5     
+ Misses       3033     3031       -2     
+ Partials      835      833       -2     

Impacted Files	Coverage Δ
x/cookie.go	100.00% <0.00%> (ø)
continuity/manager_cookie.go	50.79% <0.00%> (+1.56%)	⬆️
persistence/sql/persister_courier.go	88.33% <0.00%> (+3.33%)	⬆️

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[vinckr]

First push was very low quality, should have been a draft PR 🙈.

I addressed your feedback, thanks for the pointers.

I am at a point now where I feel it is ready to be looked at again.

[vinckr]

Deleted UPGRADE.md and addressed the other feedback 👍

[aeneasr]

Great job @vinckr ! The plan is 👍

[aeneasr]

@vinckr could you do this for the other projects as well?

[vinckr]

@vinckr could you do this for the other projects as well?

On the list 👍