feat(button): implementa o método que habilita o foco

Implementa o método que habilita o foco no `po-button`.

Fixes DTHFUI-1720

Author: nicoleoliveira

projects/ui/src/lib/components/po-button/po-button.component.html

@@ -1,4 +1,5 @@
 <button
+  #button
   class="po-button po-text-ellipsis"
   type="button"
   [class.po-button-danger]="type === 'danger'"

projects/ui/src/lib/components/po-button/po-button.component.spec.ts

@@ -130,6 +130,24 @@ describe('PoButtonComponent: ', () => {
 
   });
 
+  describe('Methods:', () => {
+
+    it('focus: should call `focus` of button', () => {
+      component.buttonElement = {
+        nativeElement: {
+          focus: () => {}
+        }
+      };
+
+      spyOn(component.buttonElement.nativeElement, 'focus');
+
+      component.focus();
+
+      expect(component.buttonElement.nativeElement.focus).toHaveBeenCalled();
+    });
+
+  });
+
   describe('Templates: ', () => {
 
     describe('Loading: ', () => {

projects/ui/src/lib/components/po-button/po-button.component.ts

@@ -1,4 +1,4 @@
-import { Component } from '@angular/core';
+import { Component, ElementRef, ViewChild } from '@angular/core';
 
 import { PoButtonBaseComponent } from './po-button-base.component';
 
@@ -27,6 +27,15 @@ import { PoButtonBaseComponent } from './po-button-base.component';
 })
 export class PoButtonComponent extends PoButtonBaseComponent {
 
+  @ViewChild('button', { static: true }) buttonElement: ElementRef;
+
+  /**
+   * Função que atribui foco ao componente.
+   */
+  focus(): void {
+    this.buttonElement.nativeElement.focus();
+  }
+
   onClick() {
     this.click.emit(null);
   }