Expose collection operations from FeedsClient

[gpunto]

Goal

AND-940

There is a new concept in town: "collections." From the doc:

Collections are data objects that can be attached to activities for managing shared data across multiple activities.

The relevant API functions got available after the latest code generation (#156), so here we're exposing them through FeedsClient.

Implementation

• Created CollectionsRepository to mirror the relevant API functions and wrapping return types in Result
• Exposed those functions through FeedsClient and implement them by delegation

Testing

Not much to test tbh, we're just delegating to the API, but if you wanted you could just call those functions on FeedsClient and check the responses

Checklist

• Issue linked (if any)
• Tests/docs updated
• I have signed the Stream CLA (required for external contributors)

[github-actions]

PR checklist ✅

All required conditions are satisfied:

• Title length is OK (or ignored by label).
• At least one pr: label exists.
• Sections ### Goal, ### Implementation, and ### Testing are filled.

🎉 Great job! This PR is ready for review.

[github-actions]

SDK Size Comparison 📏

SDK	Before	After	Difference	Status
stream-feeds-android-client	2.39 MB	2.40 MB	0.00 MB	🟢

[VelikovPetar]

Small remark about some KDocs, otherwise looks good!

[sonarqubecloud]

Quality Gate passed

Issues
6 New issues
0 Accepted issues

Measures
0 Security Hotspots
86.8% Coverage on New Code
0.1% Duplication on New Code

See analysis details on SonarQube Cloud