Test infrastructure for C# Azure Function testing (#2055)

Add support for function tests and the ability to run them against either real Azure Storage or the Azurite emulator.

See follow-up PR #2032 for actual usage.

src/ApiService/Tests/Integration/AzureStorage.cs

@@ -0,0 +1,63 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Microsoft.OneFuzz.Service;
+
+using Async = System.Threading.Tasks;
+
+namespace Tests.Integration;
+
+// This exists solely to allow use of a fixed storage account in integration tests
+// against live Azure Storage.
+sealed class AzureStorage : IStorage {
+    public static IStorage FromEnvironment() {
+        var accountName = Environment.GetEnvironmentVariable("AZURE_ACCOUNT_NAME");
+        var accountKey = Environment.GetEnvironmentVariable("AZURE_ACCOUNT_KEY");
+
+        if (accountName is null) {
+            throw new Exception("AZURE_ACCOUNT_NAME must be set in environment to run integration tests");
+        }
+
+        if (accountKey is null) {
+            throw new Exception("AZURE_ACCOUNT_KEY must be set in environment to run integration tests");
+        }
+
+        return new AzureStorage(accountName, accountKey);
+    }
+
+    public string? AccountName { get; }
+    public string? AccountKey { get; }
+
+    public AzureStorage(string? accountName, string? accountKey) {
+        AccountName = accountName;
+        AccountKey = accountKey;
+    }
+
+    public IEnumerable<string> CorpusAccounts() {
+        throw new System.NotImplementedException();
+    }
+
+    public IEnumerable<string> GetAccounts(StorageType storageType) {
+        throw new System.NotImplementedException();
+    }
+
+    public string GetPrimaryAccount(StorageType storageType) {
+        throw new System.NotImplementedException();
+    }
+
+    public Task<(string?, string?)> GetStorageAccountNameAndKey(string accountId)
+        => Async.Task.FromResult((AccountName, AccountKey));
+
+    public Task<string?> GetStorageAccountNameAndKeyByName(string accountName) {
+        throw new System.NotImplementedException();
+    }
+
+    public Uri GetTableEndpoint(string accountId)
+        => new($"https://{AccountName}.table.core.windows.net/");
+
+    public Uri GetQueueEndpoint(string accountId)
+        => new($"https://{AccountName}.queue.core.windows.net/");
+
+    public Uri GetBlobEndpoint(string accountId)
+        => new($"https://{AccountName}.blob.core.windows.net/");
+}