Add support defining Availability with annotated method

- This is for new annotation model
- @CommandAvailability which takes names of
  AvailabilityProvider beans supplying Availability info.
- Relates #663

spring-shell-samples/src/main/java/org/springframework/shell/samples/e2e/AvailabilityCommands.java

@@ -0,0 +1,123 @@
+/*
+ * Copyright 2023 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.shell.samples.e2e;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.shell.Availability;
+import org.springframework.shell.AvailabilityProvider;
+import org.springframework.shell.command.CommandRegistration;
+import org.springframework.shell.command.annotation.Command;
+import org.springframework.shell.command.annotation.CommandAvailability;
+import org.springframework.shell.standard.ShellComponent;
+import org.springframework.shell.standard.ShellMethod;
+import org.springframework.shell.standard.ShellMethodAvailability;
+import org.springframework.stereotype.Component;
+
+public class AvailabilityCommands {
+
+	@ShellComponent
+	public static class LegacyAnnotation extends BaseE2ECommands {
+
+		// find from <methodName>Availability
+		@ShellMethod(key = LEGACY_ANNO + "availability-1", group = GROUP)
+		public String testAvailability1LegacyAnnotation(
+		) {
+			return "Hello";
+		}
+
+		public Availability testAvailability1LegacyAnnotationAvailability() {
+			return Availability.unavailable("not available 1");
+		}
+
+		// find from method name in @ShellMethodAvailability
+		@ShellMethod(key = LEGACY_ANNO + "availability-2", group = GROUP)
+		@ShellMethodAvailability("testAvailability2LegacyAnnotationAvailability2")
+		public String testAvailability2LegacyAnnotation(
+		) {
+			return "Hello";
+		}
+
+		public Availability testAvailability2LegacyAnnotationAvailability2() {
+			return Availability.unavailable("not available 2");
+		}
+
+		// find backwards from @ShellMethodAvailability command name
+		@ShellMethod(key = LEGACY_ANNO + "availability-3", group = GROUP)
+		public String testAvailability3LegacyAnnotation(
+		) {
+			return "Hello";
+		}
+
+		@ShellMethodAvailability("e2e anno availability-3")
+		public Availability testAvailability3LegacyAnnotationAvailability3() {
+			return Availability.unavailable("not available 3");
+		}
+	}
+
+	@Command(command = BaseE2ECommands.ANNO, group = BaseE2ECommands.GROUP)
+	public static class Annotation extends BaseE2ECommands {
+
+		@Command(command = "availability-1")
+		@CommandAvailability(name = "testAvailability1AnnotationAvailability")
+		public String testAvailability1Annotation(
+		) {
+			return "Hello";
+		}
+
+		@Bean
+		public AvailabilityProvider testAvailability1AnnotationAvailability() {
+			return () -> Availability.unavailable("not available");
+		}
+	}
+
+	@Component
+	public static class Registration extends BaseE2ECommands {
+
+		@Bean
+		public CommandRegistration testAvailability1Registration() {
+			return getBuilder()
+				.command(REG, "availability-1")
+				.group(GROUP)
+				.availability(() -> {
+					return Availability.unavailable("not available");
+				})
+				.withTarget()
+					.function(ctx -> {
+						return "Hello";
+					})
+					.and()
+				.build();
+		}
+
+		@Bean
+		public CommandRegistration testAvailability2Registration() {
+			return getBuilder()
+				.command(REG, "availability-2")
+				.group(GROUP)
+				.availability(testAvailability2AnnotationAvailability())
+				.withTarget()
+					.function(ctx -> {
+						return "Hello";
+					})
+					.and()
+				.build();
+		}
+
+		AvailabilityProvider testAvailability2AnnotationAvailability() {
+			return () -> Availability.unavailable("not available");
+		}
+	}
+}