Rename m_SessionName => m_ServiceType and add docs

Assets/Scenes/ARCollaborationData/ARCollaborationDataExample.unity

   m_Script: {fileID: 11500000, guid: a7c1d01ad3d754ef788a30c12b724743, type: 3}
   m_Name: 
   m_EditorClassIdentifier: 
-  m_ARSession: {fileID: 0}
-  m_SessionName: arf-collab-demo
+  m_ServiceType: arf-collab-demo
 --- !u!1 &1564081113
 GameObject:
   m_ObjectHideFlags: 0

Assets/Scenes/ARCollaborationData/CollaborativeSession.cs

 public class CollaborativeSession : MonoBehaviour
 {
     [SerializeField]
-    string m_SessionName;
+    [Tooltip("The name for this network service. It should be 15 characters or less and can contain ASCII, lowercase letters, numbers, and hyphens.")]
+    string m_ServiceType;
-    public string sessionName
+    /// <summary>
+    /// The name for this network service.
+    /// See <a href="https://developer.apple.com/documentation/multipeerconnectivity/mcnearbyserviceadvertiser">MCNearbyServiceAdvertiser</a>
+    /// for the purpose of and restrictions on this name.
+    /// </summary>
+    public string serviceType
-        get { return m_SessionName; }
-        set { m_SessionName = value; }
+        get { return m_ServiceType; }
+        set { m_ServiceType = value; }
     }
 
     ARSession m_ARSession;
     void Awake()
     {
         m_ARSession = GetComponent<ARSession>();
-        m_MCSession = new MCSession(SystemInfo.deviceName, m_SessionName);
+        m_MCSession = new MCSession(SystemInfo.deviceName, m_ServiceType);
     }
 
     void OnEnable()