AuthElement to handle form submission

[samco]

One option for implementation of #14.

Implementors must define the model and primary key types, the form to bind the submitted primary key, a method to determine if the submission should be authorised and three methods to handle various outcomes of the form binding, model loading and authorisation. A different trait implementation is required for each combination of model type and authorisation rule.

I have assumed each model can be identified by a single primary key but have allowed the form to specify the name of the primary key element, its type and any validation rules that may be required.

Suggestions and improvements are welcome.

[gakuzzzz]

Hi, thanks for sending proposal and PR.

However, this FormSubmissionAuthElement seems difficult to use with other non-POST Actions in the same controller.
And Form handling can not custom by Action.

We needs dynamic creation of Authority object from POST parameters.
so we still consider the better way.