Add example of bulk import

examples/bulk-import/BulkImport.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.0.31903.59
+MinimumVisualStudioVersion = 10.0.40219.1
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+EndGlobal

examples/bulk-import/BulkImport/BulkImport.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\src\Authzed.Net\Authzed.Net.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Grpc.Core" Version="2.46.6" />
+  </ItemGroup>
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

examples/bulk-import/BulkImport/Program.cs

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+/*
+ * This is intended to be a (somewhat) real-world example of
+ * ImportBulkRelationships usage. It demonstrates chunking both across
+ * requests and within the request to optimize both for transaction
+ * size and network traffic.
+ */
+using Authzed.Api.V1;
+using Grpc.Net.Client;
+using Grpc.Core;
+
+var TOKEN = "sometoken";
+
+var TOTAL_RELATIONSHIPS_TO_WRITE = 1000;
+var RELATIONSHIPS_PER_TRANSACTION = 100;
+var RELATIONSHIPS_PER_REQUEST_CHUNK = 10;
+
+// A function that returns an iterator, which we'll use to generate our imported relationships.
+IEnumerable<Relationship> GetRelationships(int numRelationships) {
+    var idx = 0;
+    while (idx < numRelationships) {
+        idx += 1;
+        yield return new Relationship{
+            Resource = new ObjectReference{ ObjectId = idx.ToString(), ObjectType = "resource"},
+            Relation = "viewer",
+            Subject = new SubjectReference{ Object = new ObjectReference{ ObjectId = "our_user", ObjectType = "user" }},
+        };
+    }
+    yield break;
+}
+
+// Set up the client
+var credentials = CallCredentials.FromInterceptor((context, metadata) =>
+        {
+        metadata.Add("Authorization", $"Bearer {TOKEN}");
+        return Task.CompletedTask;
+        });
+
+var options = new GrpcChannelOptions
+{
+    UnsafeUseInsecureChannelCallCredentials = true,
+                                            Credentials = ChannelCredentials.Create(ChannelCredentials.Insecure, credentials),
+};
+
+var channel = GrpcChannel.ForAddress("http://localhost:50051", options);
+
+var schemaService = new SchemaService.SchemaServiceClient(channel);
+var permissionsService = new PermissionsService.PermissionsServiceClient(channel);
+
+// Write a schema
+var schema = @"
+    definition user {}
+    definition resource {
+        relation viewer: user
+        permission view = viewer
+    }
+";
+
+await schemaService.WriteSchemaAsync(new WriteSchemaRequest { Schema = schema });
+
+// Start by breaking the full list into a sequence of chunks where each chunk fits easily
+// into a datastore transaction.
+var transactionChunks = GetRelationships(TOTAL_RELATIONSHIPS_TO_WRITE).Chunk(RELATIONSHIPS_PER_TRANSACTION);
+
+foreach (var relationshipsForRequest in transactionChunks) {
+    // For each of those transaction chunks, break it down further into chunks that
+    // optimize for network throughput.
+    var requestChunks = relationshipsForRequest.Chunk(RELATIONSHIPS_PER_REQUEST_CHUNK);
+    // Open up a client stream to the server for this transaction chunk
+    using var importCall = permissionsService.ImportBulkRelationships();
+    foreach (var requestChunk in requestChunks) {
+        // For each network chunk, write to the client stream.
+        // NOTE: this makes the calls sequentially rather than concurrently; this could be
+        // optimized further by using tasks.
+        await importCall.RequestStream.WriteAsync(new ImportBulkRelationshipsRequest{
+                Relationships = { requestChunk }
+                });
+    }
+    // When we're done with the transaction chunk, complete the call and process the response.
+    await importCall.RequestStream.CompleteAsync();
+    var importResponse = await importCall;
+    Console.WriteLine("request successful");
+    Console.WriteLine(importResponse.NumLoaded);
+    // Repeat!
+}