add dividerless attribute to expansion tile

Description

Add dividerless (boolean) attribute to ExpansionTile to allow for transparent dividers between tiles.

Fixes #4303

Test Code

import flet as ft

def main(page: ft.Page):
    page.spacing = 0
    page.padding = 0

    def handle_expansion_tile_change(e):
        page.open(
            ft.SnackBar(
                ft.Text(f"ExpansionTile was {'expanded' if e.data=='true' else 'collapsed'}"),
                duration=1000,
            )
        )
        if e.control.trailing:
            e.control.trailing.name = (
                ft.icons.ARROW_DROP_DOWN
                if e.control.trailing.name == ft.icons.ARROW_DROP_DOWN_CIRCLE
                else ft.icons.ARROW_DROP_DOWN_CIRCLE
            )
            page.update()

    page.add(
        ft.ExpansionTile(
            title=ft.Text("ExpansionTile 1"),
            subtitle=ft.Text("Trailing expansion arrow icon"),
            affinity=ft.TileAffinity.PLATFORM,
            maintain_state=True,
            collapsed_text_color=ft.colors.RED,
            text_color=ft.colors.RED,
            controls=[ft.ListTile(title=ft.Text("This is sub-tile number 1"))],
            dividerless=True
        ),
        ft.ExpansionTile(
            title=ft.Text("ExpansionTile 2"),
            subtitle=ft.Text("Custom expansion arrow icon"),
            trailing=ft.Icon(ft.icons.ARROW_DROP_DOWN),
            collapsed_text_color=ft.colors.GREEN,
            text_color=ft.colors.GREEN,
            on_change=handle_expansion_tile_change,
            controls=[ft.ListTile(title=ft.Text("This is sub-tile number 2"))],
            dividerless=True
        ),
        ft.ExpansionTile(
            title=ft.Text("ExpansionTile 3"),
            subtitle=ft.Text("Leading expansion arrow icon"),
            affinity=ft.TileAffinity.LEADING,
            initially_expanded=True,
            collapsed_text_color=ft.colors.BLUE,
            text_color=ft.colors.BLUE,
            controls=[
                ft.ListTile(title=ft.Text("This is sub-tile number 3")),
                ft.ListTile(title=ft.Text("This is sub-tile number 4")),
                ft.ListTile(title=ft.Text("This is sub-tile number 5")),
            ],
            dividerless=True
        ),
    )

ft.app(main)

Type of change

[x] New feature (non-breaking change which adds functionality)
[x] This change requires a documentation update

Checklist:

[x] I signed the CLA.
[x] My code follows the style guidelines of this project
[x] I have performed a self-review of my own code
[x] My changes generate no new warnings
[x] New and existing tests pass locally with my changes
[ ] I have made corresponding changes to the documentation (if applicable)

Screenshots (if applicable):

Additional details

Summary by Sourcery

Add a 'dividerless' attribute to the ExpansionTile component to enable transparent dividers between tiles, enhancing customization options.

New Features:

Introduce a 'dividerless' boolean attribute to the ExpansionTile component, allowing for transparent dividers between tiles.

Documentation:

Update documentation to include information about the new 'dividerless' attribute for the ExpansionTile component.

flet-dev / flet

add dividerless attribute to expansion tile #4310