docs: add initial project documentation for Condado Newsletter Bot

CLAUDE.md

@@ -0,0 +1,147 @@
+# Condado Newsletter Bot
+
+A newsletter bot built with **Kotlin** and **Spring Boot**. This file gives Claude persistent
+instructions and context about the project so every session starts with the right knowledge.
+
+---
+
+## Project Overview
+
+- **Language:** Kotlin (JVM)
+- **Framework:** Spring Boot 3.x
+- **Purpose:** Automate the creation, management, and delivery of newsletters
+- **Architecture:** REST API backend with scheduled jobs for sending newsletters
+
+---
+
+## Tech Stack
+
+| Layer         | Technology                        |
+|---------------|-----------------------------------|
+| Language      | Kotlin                            |
+| Framework     | Spring Boot 3.x                   |
+| Build Tool    | Gradle (Kotlin DSL - `build.gradle.kts`) |
+| Database      | PostgreSQL (via Spring Data JPA)  |
+| Email         | Spring Mail (SMTP / JavaMailSender) |
+| Scheduler     | Spring `@Scheduled` tasks         |
+| Testing       | JUnit 5 + MockK                   |
+| Docs          | Springdoc OpenAPI (Swagger UI)    |
+
+---
+
+## Project Structure
+
+```
+src/
+├── main/
+│   ├── kotlin/com/condado/newsletter/
+│   │   ├── CondadoNewsletterApplication.kt   # App entry point
+│   │   ├── config/                           # Spring configuration classes
+│   │   ├── controller/                       # REST controllers
+│   │   ├── service/                          # Business logic
+│   │   ├── repository/                       # Spring Data JPA repositories
+│   │   ├── model/                            # JPA entities
+│   │   ├── dto/                              # Data Transfer Objects
+│   │   └── scheduler/                        # Scheduled tasks
+│   └── resources/
+│       ├── application.yml                   # Main config
+│       ├── application-dev.yml               # Dev profile config
+│       └── templates/                        # Email HTML templates (Thymeleaf)
+└── test/
+    └── kotlin/com/condado/newsletter/        # Tests mirror main structure
+```
+
+---
+
+## Build & Run Commands
+
+```bash
+# Build the project
+./gradlew build
+
+# Run the application (dev profile)
+./gradlew bootRun --args='--spring.profiles.active=dev'
+
+# Run all tests
+./gradlew test
+
+# Run a specific test class
+./gradlew test --tests "com.condado.newsletter.service.NewsletterServiceTest"
+
+# Generate OpenAPI docs (served at /swagger-ui.html when running)
+./gradlew bootRun
+```
+
+---
+
+## Coding Standards
+
+- Use **Kotlin idiomatic** style: data classes, extension functions, and null-safety operators.
+- Prefer `val` over `var` wherever possible.
+- Use **constructor injection** for dependencies (never field injection with `@Autowired`).
+- All DTOs must be **data classes** with validation annotations (`javax.validation`).
+- Controller methods must return `ResponseEntity<T>` with explicit HTTP status codes.
+- Services must be annotated with `@Service` and **never** depend on controllers.
+- Repositories must extend `JpaRepository<Entity, IdType>`.
+- Use `@Transactional` on service methods that modify data.
+- All public functions must have **KDoc** comments.
+- Use **`snake_case`** for database columns and **`camelCase`** for Kotlin properties.
+- Keep controllers thin — business logic belongs in services.
+
+---
+
+## Naming Conventions
+
+| Artifact       | Convention                        | Example                     |
+|----------------|-----------------------------------|-----------------------------|
+| Classes        | PascalCase                        | `NewsletterService`         |
+| Functions      | camelCase                         | `sendNewsletter()`          |
+| Variables      | camelCase                         | `subscriberList`            |
+| Constants      | SCREAMING_SNAKE_CASE              | `MAX_RETRIES`               |
+| DB tables      | snake_case (plural)               | `newsletter_subscribers`    |
+| REST endpoints | kebab-case                        | `/api/v1/newsletter-issues` |
+| Packages       | lowercase                         | `com.condado.newsletter`    |
+
+---
+
+## Testing Guidelines
+
+- Every service class must have a corresponding unit test class.
+- Use **MockK** for mocking (not Mockito).
+- Integration tests use `@SpringBootTest` and an **H2 in-memory** database.
+- Test method names follow the pattern: `should_[expectedBehavior]_when_[condition]`.
+- Minimum 80% code coverage for service classes.
+
+---
+
+## Environment Variables
+
+| Variable              | Description                       |
+|-----------------------|-----------------------------------|
+| `SPRING_DATASOURCE_URL`   | PostgreSQL connection URL     |
+| `SPRING_DATASOURCE_USERNAME` | DB username                |
+| `SPRING_DATASOURCE_PASSWORD` | DB password                |
+| `MAIL_HOST`           | SMTP host                         |
+| `MAIL_PORT`           | SMTP port                         |
+| `MAIL_USERNAME`       | SMTP username                     |
+| `MAIL_PASSWORD`       | SMTP password                     |
+
+> ⚠️ Never hardcode credentials. Always use environment variables or a `.env` file (gitignored).
+
+---
+
+## Key Domain Concepts
+
+- **Subscriber:** A person who opted in to receive newsletters.
+- **NewsletterIssue:** A single newsletter edition with a subject and HTML body.
+- **Campaign:** A scheduled or triggered dispatch of a `NewsletterIssue` to a group of subscribers.
+- **SendLog:** A record of each email send attempt (status: PENDING / SENT / FAILED).
+
+---
+
+## Git Workflow
+
+- Branch naming: `feature/<short-description>`, `fix/<short-description>`, `chore/<short-description>`
+- Commit messages follow [Conventional Commits](https://www.conventionalcommits.org/): `feat:`, `fix:`, `chore:`, `docs:`, `test:`
+- PRs require at least one passing CI check before merging.
+- Never commit directly to `main`.