Provide more context in `ValidationError` object

[rockacola]

Proposal:

• Include concerning attribute type (eg/ position)
• Include concerning attribute property name (eg/ role_name)
• Include a key of failed validation rule (eg/ max_length)

With above, we can allow front end to construct a more user-friendly message to describe the cause of error.

[rockacola]

Roll the consideration forward to future release.

[rockacola]

Complete as per release v0.17.0.