feat: add the ability to build policies from a map with a :type

[k13gomez]

This PR introduces map-based policy building, allowing policies to be defined using plain Clojure maps with a :type key (e.g., {:type :retry :max-retries 3}). All six policy types (:retry, :circuit-breaker, :fallback, :timeout, :rate-limiter, :bulkhead) are supported and can be used directly with execute, execute-async, and executor functions. This enables configuration-driven setups where policies can be loaded from config files, environment variables, or other data sources.

Additionally, a new policies function is provided for explicitly creating reusable policy lists from regular policies, map-based policies, or mixed combinations. The implementation moves policy logic to failsage.impl (maintaining API compatibility via potemkin/import-vars) and extends the IPolicyBuilder protocol to support the Map interface. Comprehensive tests, documentation, and examples have been added for both features.

[gemini-code-assist]

Summary of Changes

Hello @k13gomez, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the flexibility and configurability of Failsage by introducing data-driven policy definitions. Users can now define resilience policies using simple Clojure maps, making it easier to manage policies from external configuration sources. This change streamlines policy creation and composition, supporting all existing policy types and integrating smoothly with current execution mechanisms, while maintaining API stability through internal refactoring.

Highlights

• Map-based Policy Building: Introduced the ability to define all six Failsafe policy types (:retry, :circuit-breaker, :fallback, :timeout, :rate-limiter, :bulkhead) using plain Clojure maps with a :type key. This enables configuration-driven policy setups and easier serialization/deserialization.
• Seamless Integration: Map-based policies can be used directly with execute, execute-async, and executor functions, and can be mixed with traditional function-based policies for flexible composition.
• New policies Function: Added a policies function to explicitly create reusable policy lists from any combination of regular policies and map-based policies.
• Internal Refactoring: Moved policy implementation functions from failsage.core to a new failsage.impl namespace. Public API compatibility is maintained using potemkin/import-vars.
• IPolicyBuilder Extension: The IPolicyBuilder protocol has been extended to support IPersistentMap, allowing for automatic policy construction from map definitions.

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[gemini-code-assist]

Code Review

This is an excellent pull request that introduces a valuable feature for defining policies from data maps. The implementation is clean, the refactoring of policy logic into failsage.impl improves code organization, and the use of potemkin/import-vars correctly maintains API compatibility. The new policies function is a thoughtful addition for creating reusable policy lists. The documentation and tests are comprehensive and of high quality. I've identified two minor areas for improvement: one to clarify a docstring and another to make the map-based policy building more robust and idiomatic. Overall, great work.