Add a sample csdl file for testing and copy to output directory

Author: MaggieKimani1

test/Microsoft.OpenApi.Tests/Microsoft.OpenApi.Tests.csproj

@@ -43,5 +43,8 @@
     <None Update="UtilityFiles\postmanCollection_ver2.json">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>
+    <None Update="UtilityFiles\Todo.xml">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
   </ItemGroup>
 </Project>

test/Microsoft.OpenApi.Tests/UtilityFiles/Todo.xml

@@ -0,0 +1,21 @@
+<edmx:Edmx xmlns:edmx="http://docs.oasis-open.org/odata/ns/edmx" Version="4.0">
+    <edmx:DataServices>
+        <Schema xmlns="http://docs.oasis-open.org/odata/ns/edm" Namespace="microsoft.graph" >
+
+            <EntityContainer Name="TodoService">
+                <EntitySet Name="Todos" EntityType="microsoft.graph.Todo">
+                </EntitySet>
+            </EntityContainer>
+
+            <EntityType Name="Todo" HasStream="true">
+                <Key>
+                    <PropertyRef Name="Id"/>
+                </Key>
+                <Property Name="Id" Type="Edm.String"/>
+                <Property Name="Logo" Type="Edm.Stream"/>
+                <Property Name="Description" Type="Edm.String"/>
+            </EntityType>
+
+        </Schema>
+    </edmx:DataServices>
+</edmx:Edmx>