Ability to add custom class in tooltip/popover (#32217)

Porting of #31834 to main.

Co-authored-by: XhmikosR <xhmikosr@gmail.com>

js/tests/unit/tooltip.spec.js

@@ -632,6 +632,61 @@ describe('Tooltip', () => {
 
       tooltipEl.dispatchEvent(createEvent('mouseover'))
     })
+
+    it('should show a tooltip with custom class provided in data attributes', done => {
+      fixtureEl.innerHTML = '<a href="#" rel="tooltip" title="Another tooltip" data-bs-custom-class="custom-class">'
+
+      const tooltipEl = fixtureEl.querySelector('a')
+      const tooltip = new Tooltip(tooltipEl)
+
+      tooltipEl.addEventListener('shown.bs.tooltip', () => {
+        const tip = document.querySelector('.tooltip')
+        expect(tip).toBeDefined()
+        expect(tip.classList.contains('custom-class')).toBeTrue()
+        done()
+      })
+
+      tooltip.show()
+    })
+
+    it('should show a tooltip with custom class provided as a string in config', done => {
+      fixtureEl.innerHTML = '<a href="#" rel="tooltip" title="Another tooltip">'
+
+      const tooltipEl = fixtureEl.querySelector('a')
+      const tooltip = new Tooltip(tooltipEl, {
+        customClass: 'custom-class custom-class-2'
+      })
+
+      tooltipEl.addEventListener('shown.bs.tooltip', () => {
+        const tip = document.querySelector('.tooltip')
+        expect(tip).toBeDefined()
+        expect(tip.classList.contains('custom-class')).toBeTrue()
+        expect(tip.classList.contains('custom-class-2')).toBeTrue()
+        done()
+      })
+
+      tooltip.show()
+    })
+
+    it('should show a tooltip with custom class provided as a function in config', done => {
+      fixtureEl.innerHTML = '<a href="#" rel="tooltip" title="Another tooltip">'
+
+      const spy = jasmine.createSpy('customClass').and.returnValue('custom-class')
+      const tooltipEl = fixtureEl.querySelector('a')
+      const tooltip = new Tooltip(tooltipEl, {
+        customClass: spy
+      })
+
+      tooltipEl.addEventListener('shown.bs.tooltip', () => {
+        const tip = document.querySelector('.tooltip')
+        expect(tip).toBeDefined()
+        expect(spy).toHaveBeenCalled()
+        expect(tip.classList.contains('custom-class')).toBeTrue()
+        done()
+      })
+
+      tooltip.show()
+    })
   })
 
   describe('hide', () => {