feat: snyk controller extension point

Add an extension point to allow third-party plugins to interact with Snyk in
the IDE.

META-INF/plugin.xml

@@ -0,0 +1,10 @@
+<idea-plugin>
+  <id>io.snyk.plugin</id>
+
+  <extensionPoints>
+    <extensionPoint
+      name="controllerLifecycleManager"
+      interface="io.snyk.plugin.extensionpoints.SnykControllerLifecycleManager"/>
+  </extensionPoints>
+
+</idea-plugin>

src/main/kotlin/io/snyk/plugin/extensionpoints/SnykController.kt

@@ -0,0 +1,20 @@
+package io.snyk.plugin.extensionpoints
+
+import com.intellij.openapi.project.Project
+import io.snyk.plugin.getSnykApiService
+import io.snyk.plugin.getSnykTaskQueueService
+import org.apache.commons.lang3.NotImplementedException
+
+// SnykController is used by third-party plugins to interact with the Snyk plugin.
+sealed class SnykController {
+    // scan enqueues a scan of the project for vulnerabilities.
+    fun scan(project: Project) {
+        getSnykTaskQueueService(project)?.scan();
+    }
+
+    // userId returns the current authenticated Snyk user's ID.
+    // If no user is authenticated, this will return null.
+    fun userId(): String? {
+        return getSnykApiService().userId;
+    }
+}

src/main/kotlin/io/snyk/plugin/extensionpoints/SnykControllerLifecycleManager.kt

@@ -0,0 +1,11 @@
+package io.snyk.plugin.extensionpoints
+
+// SnykControllerLifecycleManager is the extension point interface
+// which other plugins can implement in order to integrate with Snyk.
+interface SnykControllerLifecycleManager {
+
+    // register is called by Snyk on third-party implementations of this interface
+    // to give the calling plugin an instance of SnykController which can be used
+    // to control Snyk in the IDE.
+    fun register(controller: SnykController)
+}