implement SkRateLimiterService with Leaky Bucket rate limiting

packages/backend/src/core/CoreModule.ts

@@ -14,6 +14,8 @@ import { AbuseReportNotificationService } from '@/core/AbuseReportNotificationSe
 import { SystemWebhookService } from '@/core/SystemWebhookService.js';
 import { UserSearchService } from '@/core/UserSearchService.js';
 import { WebhookTestService } from '@/core/WebhookTestService.js';
+import { TimeService } from '@/core/TimeService.js';
+import { EnvService } from '@/core/EnvService.js';
 import { AccountMoveService } from './AccountMoveService.js';
 import { AccountUpdateService } from './AccountUpdateService.js';
 import { AnnouncementService } from './AnnouncementService.js';
@@ -381,6 +383,8 @@ const $SponsorsService: Provider = { provide: 'SponsorsService', useExisting: Sp
 		ChannelFollowingService,
 		RegistryApiService,
 		ReversiService,
+		TimeService,
+		EnvService,
 
 		ChartLoggerService,
 		FederationChart,
@@ -680,6 +684,8 @@ const $SponsorsService: Provider = { provide: 'SponsorsService', useExisting: Sp
 		ChannelFollowingService,
 		RegistryApiService,
 		ReversiService,
+		TimeService,
+		EnvService,
 
 		FederationChart,
 		NotesChart,

packages/backend/src/core/EnvService.ts

@@ -0,0 +1,20 @@
+/*
+ * SPDX-FileCopyrightText: hazelnoot and other Sharkey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Injectable } from '@nestjs/common';
+
+/**
+ * Provides access to the process environment variables.
+ * This exists for testing purposes, so that a test can mock the environment without corrupting state for other tests.
+ */
+@Injectable()
+export class EnvService {
+	/**
+	 * Passthrough to process.env
+	 */
+	public get env() {
+		return process.env;
+	}
+}

packages/backend/src/core/TimeService.ts

@@ -0,0 +1,27 @@
+/*
+ * SPDX-FileCopyrightText: hazelnoot and other Sharkey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Injectable } from '@nestjs/common';
+
+/**
+ * Provides abstractions to access the current time.
+ * Exists for unit testing purposes, so that tests can "simulate" any given time for consistency.
+ */
+@Injectable()
+export class TimeService {
+	/**
+	 * Returns Date.now()
+	 */
+	public get now() {
+		return Date.now();
+	}
+
+	/**
+	 * Returns a new Date instance.
+	 */
+	public get date() {
+		return new Date();
+	}
+}