Introduce custom cache client support.

• Introduction of unit.WithCacheClient options that allows consumers to provide their own cache clients.
• Rename the work.UnitLogger and work.UnitScope to work.UnitZapLogger and work.UnitTallyMetricScope.
• Unexport properties of work.UnitOptions.
• Bump various dependencies:
  • github.com/stretchr/testify from 1.8.1 to 1.8.2 in /v4
  • github.com/stretchr/testify from 1.8.1 to 1.8.2 in /v3
  • github.com/avast/retry-go/v4 from 4.1.0 to 4.3.3 in /v4
  • github.com/uber-go/tally/v4 from 4.1.3 to 4.1.6 in /v4
  • go.uber.org/multierr from 1.8.0 to 1.9.0 in /v4
  • go.uber.org/multierr from 1.8.0 to 1.9.0 in /v3
  • go.uber.org/zap from 1.23.0 to 1.24.0 in /v4

Introduce InsertFunc, UpdateFunc, and DeleteFunc options.

• Introduce unit.InsertFunc, unit.UpdateFunc, and unit.DeleteFunc options.
• Refactored internals to to use unit.DataMapperFunc instead of unit.DataMapper.
• Removed DataMappers property from unit.Options.
• Renamed work.DataMapper to work.UnitDataMapper for consistency.

Introduce work unit caching.

• Introduces the work unit cache.
  • Each time the Register method is called, the provided entities will be placed in a cache if deemed eligible (have implemented the identifierer or ider interfaces).
  • Entities will be removed from the cache if specified to Alter or Remove.

Dependency upgrades to address vulnerability alerts.

• Various dependency upgrades to address vulnerability alerts.
  • Upgraded github.com/uber-go/tally dependency to version v3.4.2.
  • Upgraded github.com/stretchr/testify dependency to version v1.8.0.
  • Upgraded go.uber.org/zap dependency to version v1.21.1.

Dependency upgrades to address vulnerability alerts.

• Various dependency upgrades to address vulnerability alerts.
  • Upgraded github.com/uber-go/tally dependency to version v3.4.2.
  • Upgraded github.com/stretchr/testify dependency to version v1.8.0.
  • Upgraded go.uber.org/zap dependency to version v1.21.1.

Introduce V4 Enhancements.

• Switch from coveralls to codecov.
• Introduce initial round of benchmarks.
• Introduce support for 4 more additional metrics.
  • unit.retry.attempt
  • unit.insert
  • unit.update
  • unit.delete
• Improve documentation & switch to pkg.go.dev.
• Introduce metric demo.
  • make demo

Introduce V4.

• Introduce unit package for aliasing.
  • Reduces API footprint.
  • Often "flows" better.
• Introduce retries and related configuration.
• Reconsolidate data mappers abstractions into single DataMapper interface.
• Introduce MapperContext.
• Alter Save to be context.Context aware.
• Refactor work.NewUnit to dynamically choose which type of work unit to
  create based on provided options.
• Reconsolidate uniter functionality.