Add CreditCard faker with comprehensive test data generation

LEARNINGS.md

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+# Development Learnings
+
+This document captures important lessons learned during development to prevent future mistakes.
+
+## Adding New Faker Providers
+
+### 1. YAML files MUST be registered in `EnFile.java`
+
+**Problem**: Creating `src/main/resources/en/*.yml` is NOT enough. Without registration, `fetchString()` calls return `null` even if the file exists.
+
+**Solution**:
+- Add filename to `FILES` list in `src/main/java/org/thejavaguy/javafaker/service/files/EnFile.java`
+- Example: `"credit_card.yml",` must be added to the list
+
+**Root cause**: The `FakeValuesService` loads YAML files through `EnFile.getFiles()` - new files are invisible until registered there.
+
+### 2. Match existing YAML array format exactly
+
+**Problem**: Using dash-based YAML list format instead of project's square bracket notation.
+
+**Wrong**:
+```yaml
+banks:
+  - "Chase"
+  - "Wells Fargo"
+```
+
+**Correct**:
+```yaml
+banks: ["Chase", "Wells Fargo"]
+```
+
+**Solution**: Always check similar files (gender.yml, demographic.yml, bank.yml) for conventions before creating new YAML files.
+
+### 3. Test incrementally, not all at once
+
+**Problem**: Creating all files (YAML, Java class, tests) before running any tests makes debugging harder.
+
+**Better approach**:
+1. Create YAML file
+2. Register in EnFile.java
+3. Run a simple test to verify YAML loads
+4. Then create Java class and full test suite
+
+**Benefit**: Catches configuration issues before writing hundreds of lines of code.
+
+---
+
+*Last updated: 2026-02-09*