Add ProviderValidators to Schema Builder for customize the behavior of CustomValidator dynamically

[GiskardB]

With the 'format' attribute of json schema we can use custom validator that must exist in build time, by adding a provider of validators, the library can give the opportunity to launch in runtime, external function on validation process. For example a javascript function or a groovy script.

[coveralls]

Coverage increased (+0.02%) to 91.568% when pulling 914f840 on GiskardB:master into a8dc686 on everit-org:master.

[erosb]

Hello @GiskardB , is this change related to any parts of the json schema specfication?

[GiskardB]

Hi @erosb, no it's a simple feature of the this library that add custom validator in runtime.

[CrCat]

Nice! This is exactly what I'm looking for to support the flexibility of customized format validation.

Basically, this also satisfy the JSON Schema specification:

Implementations MAY support custom format attributes. Save for agreement between parties, schema authors SHALL NOT expect a peer implementation to support such custom format attributes. An implementation MUST NOT fail validation or cease processing due to an unknown format attribute. When treating "format" as an annotation, implementations SHOULD collect both known and unknown format attribute values.