Introduce Leader Election

This MR introduces a simple leader election based on the corresponding Fabric8 API.

Closes #228 (closed)

theodolite-quarkus/src/main/kotlin/theodolite/execution/operator/LeaderElector.kt

+package theodolite.execution.operator
+
+import io.fabric8.kubernetes.client.DefaultKubernetesClient
+import io.fabric8.kubernetes.client.NamespacedKubernetesClient
+import io.fabric8.kubernetes.client.extended.leaderelection.LeaderCallbacks
+import io.fabric8.kubernetes.client.extended.leaderelection.LeaderElectionConfigBuilder
+import io.fabric8.kubernetes.client.extended.leaderelection.resourcelock.LeaseLock
+import mu.KotlinLogging
+import java.time.Duration
+import java.util.*
+import kotlin.reflect.KFunction0
+
+private val logger = KotlinLogging.logger {}
+
+class LeaderElector(
+    val client:  NamespacedKubernetesClient,
+    val name: String
+    ) {
+
+    fun getLeadership(leader: KFunction0<Unit>) {
+        val lockIdentity: String = UUID.randomUUID().toString()
+            DefaultKubernetesClient().use { kc ->
+                kc.leaderElector()
+                .withConfig(
+                    LeaderElectionConfigBuilder()
+                        .withName("Theodolite")
+                        .withLeaseDuration(Duration.ofSeconds(15L))
+                        .withLock(LeaseLock(client.namespace, name, lockIdentity))
+                        .withRenewDeadline(Duration.ofSeconds(10L))
+                        .withRetryPeriod(Duration.ofSeconds(2L))
+                        .withLeaderCallbacks(LeaderCallbacks(
+                            { Thread{leader()}.start() },
+                            { logger.info { "STOPPED LEADERSHIP" } }
+                        ) { newLeader: String? ->
+                           logger.info { "New leader elected $newLeader" }
+                        })
+                        .build()
+                )
+                .build().run()
+        }
+    }
+
+}
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