Add architectural decision records (ADR) documentation

docs/adr/01-cryptographic-libraries.md

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+# Cryptographic libraries
+
+## Decision
+
+This project tries to avoid implementing cryptographic primitives, favouring the reuse of existing, well-tested libraries.
+
+## Rationale
+
+Cryptography is hard to get right and making a mistake when implementing a cryptographic primitive will have serious implications for the security of protocols that build upon those primitives.

docs/adr/02-test-coverage.md

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+# Test coverage
+
+## Decision
+
+This project will aim for >70% test coverage overall
+
+## Rationale
+
+A high degree of test coverage leads to more robust code and given our use of AI assisted programming helps to reduce the effect of hallucination.

docs/adr/03-any.md

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+# any instead of interface{}
+
+## Decision
+
+We use the newer 'any' instead of 'interface{}' to represent a value that can have any type.
+
+## Rationale
+
+- Functionality: Both any and interface{} can hold values of any type.
+- Interchangeability: They can be used interchangeably in code.
+- Readability: any is generally considered more readable, especially for newcomers to Go.
+- Compiler treatment: The compiler treats them identically.

docs/adr/04-ttlcache.md

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+# Caching
+
+## Decision
+
+We use the ttlcache library to provide caching across the project
+
+## Rationale
+
+A single implementation of a central concept serves to simplify the code and make caching behaviour more consistent

docs/adr/README.md

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+# ADR
+
+This directory contains the architectural decision records for the vc project
+
+About ADRs: https://github.com/joelparkerhenderson/architecture-decision-record?tab=readme-ov-file#what-is-an-architecture-decision-record