Feature - Add global error message support

[steverhoades]

This PR adds global message support, similar to functionality provided by ngx-formly.

The goals of this PR are as follows.

• Reduce boilerplate by defining all Error Message in a global scope.
• Allow for overriding a global message on a per control basis
• Support dynamic server side error messages on a per control basis without the need for AsyncValidators (Does not replace AsyncValidators)
  .
• Support function rendered messages

Example Usage:

// app.module.ts
providers: [
  {
    provide: DYNAMIC_GLOBAL_ERROR_MESSAGES,
    useValue: new Map([
      ['*', (label: string, error: string) => error] // show any undefined message
    ]),
  },
]

For the moment some additional "gymnastics" is required in order to get the controls to render the messages. See an example of that below.
//form.component.ts

 // errors comes from server call
const errors = {
    'fieldID' => {serverValidationError: 'Your field failed to pass validation' }
}
// find each control and set the errors on them.
const keys = Object.keys(errors);

keys.forEach((key) => {
  this.group.controls[key].setErrors(errors[key]);
});

// without the following the errors will not be displayed on the form.
this.formService.detectChanges(this.formComponent);

The model definition still requires that we "opt-in" to error messages.

new DynamicInputModel({
  id: 'myInput',
  label: 'My Input',
  value: '',
  errorMessages: {} //opt-in by creating an empty object
})

The result will be a control which shows the "catch-all" error message received from the server.

Room for improvements.

• Automatically mark each control for re-render once an error has been detected
• Have an explicit opt-in for showing error messages instead of relying on the existence of an errorMessages object on the model.

Use Cases:
Given that I am defining multiple forms
When I configure the validation rules
Then I should not have to repeat the errorMessages for each input in order for the messages to display on the control.

Given that I am defining a form
When I configure the validation rules
Then I should be able to process the error via a callback before returning the error message.

Given that I submit a form to the server
When the server returns a 422 response code with validation errors mapped to attribute name
Then show the error contextually on the form.

[codecov-io]

Codecov Report

Merging #1054 into master will decrease coverage by 0.01%.
The diff coverage is 80%.

@@            Coverage Diff             @@
##           master    #1054      +/-   ##
==========================================
- Coverage   90.49%   90.47%   -0.02%     
==========================================
  Files         170      170              
  Lines        2673     2678       +5     
  Branches      247      250       +3     
==========================================
+ Hits         2419     2423       +4     
  Misses        196      196              
- Partials       58       59       +1

Impacted Files	Coverage Δ
...ms/core/src/lib/service/dynamic-form-validators.ts	100% <100%> (ø)	⬆️
...src/lib/service/dynamic-form-validation.service.ts	88.15% <77.77%> (-0.74%)	⬇️

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