chore: add the source ID to the register events API request (#84)

Bucketeer/Sources/Internal/Remote/RequestBody/RegisterEventsRequestBody.swift

@@ -1,6 +1,16 @@
 import Foundation
 
 struct RegisterEventsRequestBody: Codable {
+    internal init(events: [Event] = [],
+                  sdkVersion: String = Version.current,
+                  sourceId: SourceID = SourceID.ios
+    ) {
+        self.events = events
+        self.sdkVersion = sdkVersion
+        self.sourceId = sourceId
+    }
+
     let events: [Event]
     let sdkVersion: String
+    let sourceId: SourceID
 }

BucketeerTests/ApiClientTests.swift

@@ -250,7 +250,8 @@ class ApiClientTests: XCTestCase {
       "type" : 3
     }
   ],
-  "sdkVersion" : "\(Version.current)"
+  "sdkVersion" : "\(Version.current)",
+  "sourceId" : 2
 }
 """
                 XCTAssertEqual(jsonString, expected)
@@ -360,7 +361,8 @@ class ApiClientTests: XCTestCase {
       "type" : 3
     }
   ],
-  "sdkVersion" : "\(Version.current)"
+  "sdkVersion" : "\(Version.current)",
+  "sourceId" : 2
 }
 """
                 XCTAssertEqual(jsonString, expected)