Add statestore example with Outbox pattern

[mcruzdev]

Description

This pull request adds examples for showing Outbox pattern with Java SDK and Spring.

https://docs.dapr.io/developing-applications/building-blocks/state-management/howto-outbox/

Issue reference

Closes #1579

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Extended the documentation

[mcruzdev]

@dapr/maintainers-java-sdk @dapr/approvers-java-sdk With this one, I can update the Dapr documentation that actually looks old.

@salaboy @cicoyle @artur-ciocanu @siri-varma (I am not sure that the @dapr/maintainers-java-sdk @dapr/approvers-java-sdk are working as expected)

[salaboy]

@mcruzdev this is amazing!! thanks so much for contributing!

[salaboy]

/LGTM

[mcruzdev]

dapr/docs related dapr/docs#4924

[siri-varma]

LGTM

[mcruzdev]

I think CI issues are related

[artur-ciocanu]

@mcruzdev love the changes! I have left a few tiny comments, my biggest concern is concurrent update to the list of events, other than that great job!

[salaboy]

@mcruzdev if you can address the comments from @artur-ciocanu we can merge this asap

[mcruzdev]

@mcruzdev if you can address the comments from @artur-ciocanu we can merge this asap

Hi @salaboy, comments addressed!

[artur-ciocanu]

Lovely PR!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.46%. Comparing base (d759c53) to head (b021cbd).
⚠️ Report is 233 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1582      +/-   ##
============================================
+ Coverage     76.91%   78.46%   +1.54%     
- Complexity     1592     1928     +336     
============================================
  Files           145      216      +71     
  Lines          4843     5860    +1017     
  Branches        562      656      +94     
============================================
+ Hits           3725     4598     +873     
- Misses          821      924     +103     
- Partials        297      338      +41     

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