Refactor of Supabase.Fetcher

[zoedsoupe]

Problem

1. Limited Extensibility for HTTP Requests: The existing Supabase.Fetcher lacked robust support for custom decoders, error parsers, and HTTP client backends, leading to potential limitations when integrating advanced use cases.
2. Missing Configurability for Supabase Services: Service-specific URLs and configurations were not seamlessly integrated into the Supabase.Fetcher.Request builder, potentially leading to inconsistent setups for applications.
3. Inconsistent Error Handling: The lack of a centralized error management system meant error messages could be fragmented and harder to debug.
4. Absence of Detailed Test Coverage: Existing tests did not fully validate the behavior of streaming, file uploads, and custom configurations.

Solution

1. Enhanced HTTP Request Builder:
   • Introduced a fully extensible request builder API in Supabase.Fetcher.Request that allows chaining methods for custom headers, body decoders, error parsers, and HTTP clients.
   • Added support for service-specific URL handlers (with__url/2) to standardize endpoint configurations for services like auth, storage, and database.
2. Improved Error Handling:
   • Centralized error management via the Supabase.Error module, defining a unified structure for error codes, messages, metadata, and service-specific origins.
   • Implemented error parsers in Supabase.ErrorParser for handling transport and HTTP errors seamlessly.
3. Streaming and File Upload Support:
   • Added robust support for streaming large files and consuming streamed responses using Finch.stream/5 in Supabase.Fetcher.Adapter.Finch.
   • Introduced file upload utilities that handle file streams, content-length headers, and MIME type detection automatically.
4. Tests for Comprehensive Coverage:
   • Enhanced test coverage with unit tests for request building, service-specific configurations, custom decoders, and error parsers.
   • Included tests for file upload, streaming, and error handling scenarios, ensuring edge cases are well-tested.
5. Documentation and Clarity:
   • Updated module and function documentation to describe key features and example use cases, making it easier for developers to adopt the changes.
   • Added clear examples for implementing custom decoders and error parsers, and using the enhanced request builder API.

Rationale

1. Developer Productivity: The improved request builder and service-specific configurations reduce boilerplate code and improve consistency across integrations.
2. Error Debugging: Centralized error handling and detailed metadata in error messages enhance troubleshooting and debugging workflows.
3. Future-Proof Design: By introducing behaviors and allowing custom implementations for HTTP clients, body decoders, and error parsers, the library becomes extensible for future needs.
4. Reliability: The expanded test coverage ensures that core features like streaming, file uploads, and error management work as expected across a variety of scenarios.
5. Alignment with Supabase Ecosystem: These changes make the library a more powerful and idiomatic choice for Elixir developers integrating with Supabase, aligning well with Supabase’s flexibility and developer-first approach.