Add Event Indexing Guide and social_feed example

[deranalabs]

Cedra Builders Forge - Submission

Season 1

📋 Task Information

Task Title: Event Indexing Guide (Issue #63)

Issue Link: #63

Telegram: @deranaz

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✅ Checklist

• Commented "I'm taking this task" on the issue before starting
• This PR contains ONE task only
• All work is original (no copy-paste)
• Code compiles without errors and all tests pass
• Includes README, tests, and documentation
• Will share PR in Cedra Builders Telegram

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📝 What Was Built

I built a complete Event Indexing Guide and an example Move Package that demonstrates how to implement gas-efficient social feeds on Cedra using events instead of on-chain vectors.

Key Features:

• Guide: README.md explains the problem of state bloat and introduces the "Events as Storage" pattern.
• Contract: Example module cedra_guide::social_feed that emits PostEvent instead of storing posts in global state.
• Tests: End-to-end Move unit test that verifies the full flow from register → post → event emission.

Technical Approach:
I created a minimal Move package CedraEventGuide with a UserEvents resource holding an EventHandle<PostEvent> per user. The post entry function only emits events and never appends to an on-chain vector, keeping gas usage low and state small.

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🧪 Testing

Setup:

# From the docs repository root
cd docs/guides/event-indexing

How to Test:

1. Ensure Aptos CLI is installed (tested with v7.11.0).
2. Run the test command:

aptos move test --skip-fetch-latest-git-deps

3. Expected Results: The command should compile AptosFramework at aptos-release-v1.9.0, build the CedraEventGuide package, and run tests successfully.

INCLUDING DEPENDENCY AptosFramework
BUILDING CedraEventGuide
Running Move unit tests
[ PASS    ] 0x...::social_feed::test_end_to_end
Test result: OK. Total tests: 1; passed: 1; failed: 0

⚠️ Note to Reviewers: The current cedra CLI (v1.0.4) ships with an older Move compiler and fails while compiling recent AptosFramework versions due to unsupported ability constraints. I verified the logic using the aptos CLI, and it is fully compatible with the Cedra Network.

📚 Documentation

• README with setup instructions
• Code comments on complex logic
• Working usage examples (Move + TypeScript event query)
• API / function behavior documented in the guide

🎯 Quality Check

I confirm my submission:

• Handles edge cases and errors properly (e.g., user must register before posting)
• Follows Move conventions and best practices
• Is gas efficient and reusable (events instead of stored vectors)
• Has clear structure and helpful error messages
• Does NOT contain plagiarism, malicious code, or spam

📸 Demo (Optional)

I have read and agree to follow all Cedra Builders Forge rules.

Closes #63