Implement Team Membership changes (#1670)

* Fixup TeamContext helper name

* Implement overload for GetAllMembers to take request parameter

* Update tests

* Implement Obersvable client changes

* Observable tests

* Implement AddOrEditMembership function returning a new response model, and obsolete the old AddMembership function returning an enum

* Implement GetMembershipDetails function returning new TeamMembershipDetails response model, and obsolete the old GetMembership function returning an enum

* Clarify that an exception is thrown when not a member

* Add integration tests for AddOrEditMembership and GetMembershipDetails

* fixup exception test for observable client

* Update wording of obsolete message

Octokit/Models/Request/TeamMembersRequest.cs

@@ -0,0 +1,55 @@
+using System.Diagnostics;
+using System.Globalization;
+using Octokit.Internal;
+
+namespace Octokit
+{
+    /// <summary>
+    /// Used to filter requests for team members
+    /// </summary>
+    [DebuggerDisplay("{DebuggerDisplay,nq}")]
+    public class TeamMembersRequest : RequestParameters
+    {
+        public TeamMembersRequest(TeamRoleFilter role)
+        {
+            Role = role;
+        }
+
+        /// <summary>
+        /// Which membership roles to get
+        /// </summary>
+        public TeamRoleFilter Role { get; private set; }
+
+        internal string DebuggerDisplay
+        {
+            get
+            {
+                return string.Format(CultureInfo.InvariantCulture, "Role {0} ", Role);
+            }
+        }
+    }
+
+    /// <summary>
+    /// Filtering by Roles within a Team
+    /// </summary>
+    public enum TeamRoleFilter
+    {
+        /// <summary>
+        /// Regular Team Member
+        /// </summary>
+        [Parameter(Value = "member")]
+        Member,
+
+        /// <summary>
+        ///  Team Maintainer
+        /// </summary>
+        [Parameter(Value = "maintainer")]
+        Maintainer,
+
+        /// <summary>
+        /// All Roles
+        /// </summary>
+        [Parameter(Value = "all")]
+        All
+    }
+}

Octokit/Models/Request/UpdateTeamMembership.cs

@@ -0,0 +1,31 @@
+using System.Diagnostics;
+using System.Globalization;
+using Octokit.Internal;
+
+namespace Octokit
+{
+    /// <summary>
+    /// Used to filter requests for team members
+    /// </summary>
+    [DebuggerDisplay("{DebuggerDisplay,nq}")]
+    public class UpdateTeamMembership
+    {
+        public UpdateTeamMembership(TeamRole role)
+        {
+            Role = role;
+        }
+
+        /// <summary>
+        /// Which membership roles to get
+        /// </summary>
+        public TeamRole Role { get; private set; }
+
+        internal string DebuggerDisplay
+        {
+            get
+            {
+                return string.Format(CultureInfo.InvariantCulture, "Role {0}", Role);
+            }
+        }
+    }
+}