Functions/Connect-SharePointOnlineAdminAccount.ps1

<#
.SYNOPSIS
    This function connects to SharePoint Online using admin account credentials or a MSPComplete Endpoint.
.DESCRIPTION
    This function connects to SharePoint Online using admin account credentials or a MSPComplete Endpoint.
    It returns whether the connection and logon was successful.
.EXAMPLE
    Connect-SharePointOnlineAdminAccount -Endpoint $Endpoint
.EXAMPLE
    $Endpoint | Connect-SharePointOnlineAdminAccount
.EXAMPLE
    Connect-SharePointOnlineAdminAccount -Username $username -Password $password -OrganizationName $organizationName
#>

function Connect-SharePointOnlineAdminAccount {
    [CmdletBinding(PositionalBinding=$false)]
    [OutputType([Bool])]
    param (
        # The username of the SharePoint Online account.
        [Parameter(Mandatory=$true, ParameterSetName="credential")]
        [ValidateNotNullOrEmpty()]
        [String]$username,

        # The password of the SharePoint Online account.
        [Parameter(Mandatory=$true, ParameterSetName="credential")]
        [ValidateNotNull()]
        [SecureString]$password,

        # The name of the organization in Office 365.
        [Parameter(Mandatory=$true, ParameterSetName="credential")]
        [ValidateNotNullOrEmpty()]
        [String]$organizationName,

        # The MSPComplete Endpoint.
        [Parameter(Mandatory=$true, ParameterSetName="endpoint", ValueFromPipeline=$true)]
        [ValidateNotNull()]
        $endpoint
    )

    # Check for existing connection
    if ($Global:SharePointOnlineConnectionEstablished) {
        Write-Warning "The connection to SharePoint Online has already been established."
        return $true
    }
    $Global:SharePointOnlineConnectionEstablished = $false

    # If given endpoint, retrieve credential directly
    if ($PSCmdlet.ParameterSetName -eq "endpoint") {
        $sharePointOnlineCredential = $endpoint.Credential
        $username = $sharePointOnlineCredential.Username
        if (!(Search-HashTable -HashTable $endpoint.ExtendedProperties -Key "OrganizationName")) {
            Write-Error "The endpoint does not have an 'OrganizationName' extended property."
            return $false
        }
        $organizationName = Search-HashTable -HashTable $endpoint.ExtendedProperties -Key "OrganizationName"
    }

    # Create the SharePoint Online credential from the given username and password
    else {
        $sharePointOnlineCredential = [PSCredential]::new($username, $password)
    }

    # Logon to SharePoint Online
    try {
        Connect-SPOService -Url "https://$($organizationName)-admin.sharepoint.com" -Credential $sharePointOnlineCredential -ErrorAction Stop

        # Logon was successful
        Write-Information "Connection and logon to SharePoint Online successful with username '$($username)'."
        $Global:SharePointOnlineConnectionEstablished = $true
        return $true
    }

    # Logon was unsuccessful
    catch {
        Write-Error "Failed SharePoint Online account login with username '$($username)'.`r`n$($_.Exception.Message)"
        return $false
    }
}