Refactor: move internal packages to pkg/ for better organization

- Moved internal/auth and internal/crypto to pkg/ directory
- Updated all import statements and dependencies
- Added new domain/oauth_errors.go and GEMINI.md
- Removed obsolete cache files
- Updated service interfaces to use domain types

Author: paalgyula

GEMINI.md

@@ -0,0 +1,93 @@
+## Project Overview
+
+This project is a Go-based OAuth 2.0 and OpenID Connect (OIDC) server called Shadow SSO (3SO). It provides a complete suite of tools to implement secure authentication and authorization in Go applications. It can be used as a standalone server or as a library.
+
+The project is designed to be modular and flexible, with support for various grant types, token management features, and integration with external identity providers like LDAP/Active Directory. It uses MongoDB for data storage by default but also offers a high-performance Distributed Token Store (DTS) backend using BBoltDB.
+
+The project also includes a command-line interface (CLI) tool called `ssoctl` for managing the SSO system.
+
+## Building and Running
+
+The project uses a `Makefile` for common development tasks.
+
+### Building
+
+To build the `ssso` server and `ssoctl` CLI applications, run:
+
+```bash
+make build
+```
+
+This will create the `ssso` and `ssoctl` executables in the project's root directory.
+
+### Running
+
+The `ssso` server can be run in several ways:
+
+**1. Standalone:**
+
+After building the application, you can run it directly:
+
+```bash
+./ssso
+```
+
+The server requires a configuration file (`sso_config.yaml`) or environment variables to be set. Key configuration options include the MongoDB connection string, issuer URL, and token signing key.
+
+**2. Docker:**
+
+A `Dockerfile` is provided to build a Docker image for the `ssso` server:
+
+```bash
+docker build -t pilab/ssso:latest .
+```
+
+You can then run the container with the required environment variables:
+
+```bash
+docker run -d \
+  -p 8080:8080 \
+  -e SSSO_MONGO_URI="mongodb://your_mongo_host:27017/shadow_sso_db" \
+  -e SSSO_ISSUER_URL="http://localhost:8080" \
+  -e SSSO_SIGNING_KEY_PATH="/path/to/your/signing_key.pem" \
+  --name ssso-server \
+  pilab/ssso:latest
+```
+
+**3. Docker Compose:**
+
+The project includes a `docker-compose.yml` file to run the `ssso` server with the Distributed Token Store (`ssso-dts`) and a MongoDB instance:
+
+```bash
+docker-compose up --build
+```
+
+### Testing
+
+To run the unit tests, use the following command:
+
+```bash
+make test
+```
+
+## Development Conventions
+
+*   **Code Generation:** The project uses Protocol Buffers and `buf` to generate Go code for API definitions. The `make proto` command can be used to regenerate the code.
+*   **Dependency Management:** Go modules are used for dependency management. The `go.mod` file lists the project's dependencies.
+*   **Configuration:** The server and CLI tool are configured using Viper, which allows for configuration via files (e.g., `sso_config.yaml`) or environment variables.
+*   **Interfaces:** The project defines several interfaces (`OAuthRepository`, `UserRepository`, `TokenStore`) to allow for custom implementations of storage and caching layers. The default implementation uses MongoDB.
+*   **CLI:** The `ssoctl` CLI is built using Cobra, a popular library for creating CLI applications in Go.
+
+## Key Files
+
+*   `README.md`: Provides a comprehensive overview of the project, its features, and how to use it.
+*   `Makefile`: Contains commands for building, testing, and other development tasks.
+*   `go.mod`: Defines the project's Go module and its dependencies.
+*   `apps/ssso/ssso.go`: The main entry point for the `ssso` server application.
+*   `apps/sssoctl/sssoctl.go`: The main entry point for the `ssoctl` CLI tool.
+*   `apps/ssso/config/config.go`: Defines the configuration structure for the `ssso` server.
+*   `domain/`: Contains the core domain models and interfaces for the application.
+*   `mongodb/`: Contains the MongoDB implementation of the repository interfaces.
+*   `services/`: Contains the business logic and services for the application.
+*   `api/`: Contains the API handlers for the server.
+*   `proto/`: Contains the Protocol Buffer definitions for the API.