Replace the ServiceLocator with direct dependency injection (#5548)

Removes the ServiceLocator singleton and instead directly injects the dependencies it was holding for more control over instantiation of the various component subtrees and better visibility over how they're being used.

UnitTests/Sources/AnalyticsTests.swift

@@ -12,18 +12,19 @@ import PostHog
 import Testing
 
 final class AnalyticsTests {
-    private var appSettings: AppSettings
-    private var analyticsClient: AnalyticsClientMock
+    private let appSettings: AppSettings
+    private let analytics: AnalyticsService
+    private let analyticsClient: AnalyticsClientMock
     private var posthogMock: PHGPostHogMock
     
+    @MainActor
     init() {
         AppSettings.resetAllSettings()
         appSettings = AppSettings()
         
         analyticsClient = AnalyticsClientMock()
         analyticsClient.isRunning = false
-        ServiceLocator.shared.register(analytics: AnalyticsService(client: analyticsClient,
-                                                                   appSettings: appSettings))
+        analytics = .mock(analyticsClient, settings: appSettings)
         
         posthogMock = PHGPostHogMock()
         posthogMock.configureMockBehavior()
@@ -37,7 +38,7 @@ final class AnalyticsTests {
     func analyticsPromptNewUser() {
         // Given a fresh install of the app (without PostHog analytics having been set).
         // When the user is prompted for analytics.
-        let showPrompt = ServiceLocator.shared.analytics.shouldShowAnalyticsPrompt
+        let showPrompt = analytics.shouldShowAnalyticsPrompt
         
         // Then the prompt should be shown.
         #expect(showPrompt, "A prompt should be shown for a new user.")
@@ -49,7 +50,7 @@ final class AnalyticsTests {
         appSettings.analyticsConsentState = .optedOut
         
         // When the user is prompted for analytics
-        let showPrompt = ServiceLocator.shared.analytics.shouldShowAnalyticsPrompt
+        let showPrompt = analytics.shouldShowAnalyticsPrompt
         
         // Then no prompt should be shown.
         #expect(!showPrompt, "A prompt should not be shown any more.")
@@ -61,7 +62,7 @@ final class AnalyticsTests {
         appSettings.analyticsConsentState = .optedIn
         
         // When the user is prompted for analytics
-        let showPrompt = ServiceLocator.shared.analytics.shouldShowAnalyticsPrompt
+        let showPrompt = analytics.shouldShowAnalyticsPrompt
         
         // Then no prompt should be shown.
         #expect(!showPrompt, "A prompt should not be shown any more.")
@@ -71,7 +72,7 @@ final class AnalyticsTests {
     func analyticsPromptNotDisplayed() {
         // Given a fresh install of the app Analytics should be disabled
         #expect(appSettings.analyticsConsentState == .unknown)
-        #expect(!ServiceLocator.shared.analytics.isEnabled)
+        #expect(!analytics.isEnabled)
         #expect(!analyticsClient.startAnalyticsConfigurationCalled)
     }
     
@@ -79,10 +80,10 @@ final class AnalyticsTests {
     func analyticsOptOut() {
         // Given a fresh install of the app (without PostHog analytics having been set).
         // When analytics is opt-out
-        ServiceLocator.shared.analytics.optOut()
+        analytics.optOut()
         // Then analytics should be disabled
         #expect(appSettings.analyticsConsentState == .optedOut)
-        #expect(!ServiceLocator.shared.analytics.isEnabled)
+        #expect(!analytics.isEnabled)
         #expect(!analyticsClient.isRunning)
         // Analytics client should have been stopped
         #expect(analyticsClient.stopCalled)
@@ -92,10 +93,10 @@ final class AnalyticsTests {
     func analyticsOptIn() {
         // Given a fresh install of the app (without PostHog analytics having been set).
         // When analytics is opt-in
-        ServiceLocator.shared.analytics.optIn()
+        analytics.optIn()
         // The analytics should be enabled
         #expect(appSettings.analyticsConsentState == .optedIn)
-        #expect(ServiceLocator.shared.analytics.isEnabled)
+        #expect(analytics.isEnabled)
         // Analytics client should have been started
         #expect(analyticsClient.startAnalyticsConfigurationCalled)
     }
@@ -105,8 +106,8 @@ final class AnalyticsTests {
         // Given an existing install of the app where the user previously declined the tracking
         appSettings.analyticsConsentState = .optedOut
         // Analytics should not start
-        #expect(!ServiceLocator.shared.analytics.isEnabled)
-        ServiceLocator.shared.analytics.startIfEnabled()
+        #expect(!analytics.isEnabled)
+        analytics.startIfEnabled()
         #expect(!analyticsClient.startAnalyticsConfigurationCalled)
     }
     
@@ -115,8 +116,8 @@ final class AnalyticsTests {
         // Given an existing install of the app where the user previously accepted the tracking
         appSettings.analyticsConsentState = .optedIn
         // Analytics should start
-        #expect(ServiceLocator.shared.analytics.isEnabled)
-        ServiceLocator.shared.analytics.startIfEnabled()
+        #expect(analytics.isEnabled)
+        analytics.startIfEnabled()
         #expect(analyticsClient.startAnalyticsConfigurationCalled)
     }
     
@@ -214,14 +215,14 @@ final class AnalyticsTests {
     func resetConsentState() {
         // Given an existing install of the app where the user previously accpeted the tracking
         appSettings.analyticsConsentState = .optedIn
-        #expect(!ServiceLocator.shared.analytics.shouldShowAnalyticsPrompt)
+        #expect(!analytics.shouldShowAnalyticsPrompt)
         
         // When forgetting analytics consents
-        ServiceLocator.shared.analytics.resetConsentState()
+        analytics.resetConsentState()
         
         // Then the analytics prompt should be presented again
         #expect(appSettings.analyticsConsentState == .unknown)
-        #expect(ServiceLocator.shared.analytics.shouldShowAnalyticsPrompt)
+        #expect(analytics.shouldShowAnalyticsPrompt)
     }
     
     @Test