reduce repeated/unnecessary code

[grosser]

just wanted to make a tiny change ... then things escalated 😭
@danielmorrison @domcleal

• make audited_attributes and audited_changes follow the same logic regarding only & except and privacy level
• remove runtime .to_s-ing of only & except
• remove duplicate non_audited_columns instance method
• remove non_audited_columns class method in favor of either calling audited except: [] or modifying audited_options
• remove unnecessary .flatten
• test actual auditing behavior instead of testing class accessors
• test actual recorded columns instead of testing for if they include certain things to make tests catch empty hashes / wrong keys

warning: records_changes_to_specified_fields? seems to be untested ... but that's for another PR

[grosser]

... I'd love to take this even further and make create + destroy also simply audit changes ... that would unify the stored data and remove redundant fields in create/destroy audits ...

[danielmorrison]

Looks good to me after a quick glance. Should we add any deprecation methods/warnings?

[grosser]

warnings just get ignores ... if someone updates this will blow up and they have to find out what to do ... could keep the method defined and raise a NotImplementedError instead though ?

[grosser]

added NotImplementedError for removed methods ... good to go ?

[grosser]

@danielmorrison

[tbrisker]

@grosser I think a lot of the complexity and duplication has been resolved in various other PRs that were recently merged. Are there some changes that are still required? If so, could you please update your PR?