9.15: Popover Custom class example
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**Primary Actor**: User

**Scope**: Ngx-bootstrap DEMO / BS version 3&4

**Goal**: Show user how make popovers with custom classes

Main success scenario:
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1. User opens Popover demo page
2. User clicks on Custom class sub-menu
3. User see clickable button "Custom class demo"
4. When user clicks on "Custom class demo", then popover-container appear above the button with specific style
5. When user clicks on "Custom class demo" again, then popover-container disappeared
6. Template src should be written with containerClass="customClass"

Variations:
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2*. User scroll to Custom class sub-menu