Improve Micro::Case#call! invalid result error messages

[serradura]

Raise a better error when the Micro::Case#call! doesn't return a Micro::Case::Result instance.

Expected exception: Micro::Case::Error::InvalidResult.

Expected messages:

Invalid success/failure result without a custom type:

The result returned from MyCase#call! must be a Hash.

Example:
  Success(result: { key: 'value' })

The result returned from MyCase#call! must be a Hash.

Example:
  Failure(result: { key: 'value' })

Invalid success/failure result with a custom type:

The result returned from MyCase#call! must be a Hash.

Example:
  Success(:my_success, result: { key: 'value' })

The result returned from MyCase#call! must be a Hash.

Example:
  Failure(:my_failure, result: { key: 'value' })

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Thanks, @MatheusRich and @mrbongiolo for helping me to elaborate on this idea. 🚀