webdav: add support for sharepoint with NTLM authentication (#2921)

Add new option option "sharepoint-ntlm" for the vendor setting.
Use it when your hosted Sharepoint is not tied to the OneDrive
accounts and uses NTLM authentication.
Also add documentation and integration test.

Fixes: #2171

backend/webdav/webdav_test.go

@@ -38,3 +38,14 @@ func TestIntegration3(t *testing.T) {
 		NilObject:  (*webdav.Object)(nil),
 	})
 }
+
+// TestIntegration runs integration tests against the remote
+func TestIntegration4(t *testing.T) {
+	if *fstest.RemoteName != "" {
+		t.Skip("skipping as -remote is set")
+	}
+	fstests.Run(t, &fstests.Opt{
+		RemoteName: "TestWebdavNTLM:",
+		NilObject:  (*webdav.Object)(nil),
+	})
+}