Add user to teams chat

PS-Rainer 

When taking a look directly at the API call used it appears that the command is New-MgChatMember:
https://learn.microsoft.com/en-us/graph/api/chat-post-members?view=graph-rest-1.0&tabs=powershell

Import-Module Microsoft.Graph.Teams

$params = @{
	"@odata.type" = "#microsoft.graph.aadUserConversationMember"
	"email address removed for privacy reasons" = "https://graph.microsoft.com/v1.0/users/8b081ef6-4792-4def-b2c9-c363a1bf41d5"
	VisibleHistoryStartDateTime = [System.DateTime]::Parse("2019-04-18T23:51:43.255Z")
	Roles = @(
		"owner"
	)
}

New-MgChatMember -ChatId $chatId -BodyParameter $params

Uh, it appears that techcommunity breaks stuff with the email protection, I recommend you look at the code directly in Microsoft Docs