Adds Trigger.nextExecution() impls

Also updates spring.version 6.0.0-SNAPSHOT

Closes gh-714

pom.xml

@@ -27,7 +27,7 @@
 		<kotlin-coroutines.version>1.6.2</kotlin-coroutines.version>
 		<mockk.version>1.10.3-jdk8</mockk.version>
 		<mockito-core.version>3.8.0</mockito-core.version>
-		<spring.version>6.0.0-M4</spring.version>
+		<spring.version>6.0.0-SNAPSHOT</spring.version>
 		<spring-data-bom.version>2022.0.0-M4</spring-data-bom.version>
 		<spring-security-bom.version>5.4.5</spring-security-bom.version>
 		<reactor.version>2020.0.13</reactor.version>

spring-vault-core/src/main/java/org/springframework/vault/authentication/LifecycleAwareSessionManagerSupport.java

@@ -16,6 +16,7 @@
 package org.springframework.vault.authentication;
 
 import java.time.Duration;
+import java.time.Instant;
 import java.util.Date;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -195,6 +196,14 @@ public abstract class LifecycleAwareSessionManagerSupport extends Authentication
 			return null;
 		}
 
+		@Override
+		public Instant nextExecution(TriggerContext triggerContext) {
+			if (this.fired.compareAndSet(false, true)) {
+				return this.nextExecutionTime.toInstant();
+			}
+
+			return null;
+		}
 	}
 
 	/**

spring-vault-core/src/main/java/org/springframework/vault/core/lease/SecretLeaseContainer.java

@@ -16,6 +16,7 @@
 package org.springframework.vault.core.lease;
 
 import java.time.Duration;
+import java.time.Instant;
 import java.util.Date;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -948,6 +949,15 @@ public class SecretLeaseContainer extends SecretLeaseEventPublisher implements I
 			return null;
 		}
 
+		@Override
+		public Instant nextExecution(TriggerContext triggerContext) {
+			if (UPDATER.compareAndSet(this, STATUS_ARMED, STATUS_FIRED)) {
+				return Instant.ofEpochMilli(System.currentTimeMillis() + TimeUnit.SECONDS.toMillis(this.seconds));
+			}
+
+			return null;
+		}
+
 	}
 
 	/**