Added ability to find a plugin by destination key.

Sources/Segment/Plugins.swift

@@ -159,4 +159,8 @@ extension Analytics {
     public func find<T: Plugin>(pluginType: T.Type) -> T? {
         return timeline.find(pluginType: pluginType)
     }
+
+    public func find(key: String) -> DestinationPlugin? {
+        return timeline.find(key: key)
+    }
 }

Sources/Segment/Timeline.swift

@@ -135,6 +135,17 @@ extension Timeline {
         }
         return found.first as? T
     }
+
+    internal func find(key: String) -> DestinationPlugin? {
+        var found = [Plugin]()
+        if let mediator = plugins[.destination] {
+            found.append(contentsOf: mediator.plugins.filter{ plugin in
+                guard let p = plugin as? DestinationPlugin else { return false }
+                return p.key == key
+            })
+        }
+        return found.first as? DestinationPlugin
+    }
 }
 
 // MARK: - Plugin Timeline Execution

Tests/Segment-Tests/Analytics_Tests.swift

@@ -76,6 +76,10 @@ final class Analytics_Tests: XCTestCase {
 
         analytics.track(name: "testDestinationEnabled")
 
+        let dest = analytics.find(key: myDestination.key)
+        XCTAssertNotNil(dest)
+        XCTAssertTrue(dest is MyDestination)
+
         wait(for: [expectation], timeout: 1.0)
     }