Need to add titiler_endpoint argument when calling cog_tile_vmin_vmax in add_cog_layer

[flyhamsw]

Fixed a problem when running add_cog_layer with custom titiler_endpoint.

When a user run add_cog_layer with custom titiler_endpoint, the user will encounter following error message.

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File ~/Desktop/workspace/leafmap/leafmap/stac.py:246, in cog_tile_vmin_vmax(url, bands, titiler_endpoint, percentile, **kwargs)
    [243](https://file+.vscode-resource.vscode-cdn.net/Users/swham/Desktop/workspace/leafmap/~/Desktop/workspace/leafmap/leafmap/stac.py:243)     stats = {s: stats[s] for s in stats if s in bands}
    [245](https://file+.vscode-resource.vscode-cdn.net/Users/swham/Desktop/workspace/leafmap/~/Desktop/workspace/leafmap/leafmap/stac.py:245) if percentile:
--> [246](https://file+.vscode-resource.vscode-cdn.net/Users/swham/Desktop/workspace/leafmap/~/Desktop/workspace/leafmap/leafmap/stac.py:246)     vmin = min([stats[s]["percentile_2"] for s in stats])
    [247](https://file+.vscode-resource.vscode-cdn.net/Users/swham/Desktop/workspace/leafmap/~/Desktop/workspace/leafmap/leafmap/stac.py:247)     vmax = max([stats[s]["percentile_98"] for s in stats])
    [248](https://file+.vscode-resource.vscode-cdn.net/Users/swham/Desktop/workspace/leafmap/~/Desktop/workspace/leafmap/leafmap/stac.py:248) else:

TypeError: string indices must be integers, not 'str'

This error is occured in leafmap.stac.cog_tile_vmin_vmax function due to wrong response from titiler. However, although the user provided the custom titiler_endpoint, this is not passed to the function, so the function tries to retrieve environment variable named TITILER_ENDPOINT. As a result, this function sends request to another URL rather than the URL that the user wants.

The problem can be simply solved by adding titiler_endpoint argument when calling leafmap.stac.cog_tile_vmin_vmax function in add_cog_layer.

[giswqs]

LGTM. Thank you for the fix.

[mergify]

Thanks for the contribution @flyhamsw 🤩