Webrequest - Authorization

Access API with OAuth 2.0 Access Token.ps1

$headers = @{}
$headers.Add('Authorization', "Bearer $accesstoken")
Invoke-RestMethod -Headers $headers -Uri  https://graph.microsoft.com/v1.0/me -Method Get

REST API Basic Authentication.ps1

# Step 1. Create a username:password pair
$plaintextCredentials = "$($username):$($password)"

# Step 2. Encode the pair to Base64 string
$encodedCredentials = [System.Convert]::ToBase64String([System.Text.Encoding]::ASCII.GetBytes($plaintextCredentials))
 
# Step 3. Form the header and add the Authorization attribute to it
$headers = @{}
$headers.Add('Authorization',"Basic $encodedCredentials")