Add API for Retrieving All Documents

[raararaara]

What this PR does / why we need it:
This PR introduces additional functionality required for the creation and retrieval of documents through REST API. Specifically, it adds the following enhancements:

• Authentication via Project Secret Key: Previously, authentication for API access was limited to user JWT tokens only. With this update, we have extended the authentication mechanism to also allow authentication using a Project Secret Key. This change provides more flexibility in how users and systems can authenticate and access our API.

Which issue(s) this PR fixes:

Related #677

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Additional documentation:

Checklist:

• Added relevant tests or not required
• Didn't break anything

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Attention: 39 lines in your changes are missing coverage. Please review.

Comparison is base (6936d2b) 49.30% compared to head (b3a9327) 50.17%.
Report is 3 commits behind head on main.

Files	Patch %	Lines
server/backend/database/mongo/client.go	8.33%	22 Missing ⚠️
server/backend/database/memory/database.go	32.00%	15 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #755      +/-   ##
==========================================
+ Coverage   49.30%   50.17%   +0.86%     
==========================================
  Files          69       69              
  Lines       10094    10165      +71     
==========================================
+ Hits         4977     5100     +123     
+ Misses       4601     4526      -75     
- Partials      516      539      +23     

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[hackerwins]

Thanks for your contribution. Overall looks good.

I left a few comments.

[hackerwins]

LGTM. 🚀