【功能新增】IoT：增加插件支持，包含插件API和示例控制器

yudao-module-iot/yudao-module-iot-plugin-api/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>cn.iocoder.boot</groupId>
+    <artifactId>yudao-module-iot-plugin-api</artifactId>
+    <version>0.0.1</version>
+    <packaging>jar</packaging>
+
+    <name>${project.artifactId}</name>
+    <description>
+        物联网 模块插件 API，暴露给其它模块调用
+    </description>
+
+    <properties>
+        <pf4j-spring.version>0.9.0</pf4j-spring.version>
+    </properties>
+
+    <dependencies>
+        <!-- PF4J Spring 集成 -->
+        <dependency>
+            <groupId>org.pf4j</groupId>
+            <artifactId>pf4j-spring</artifactId>
+            <version>${pf4j-spring.version}</version>
+            <scope>provided</scope>
+        </dependency>
+    </dependencies>
+
+</project>

yudao-module-iot/yudao-module-iot-plugin-api/src/main/java/cn/iocoder/yudao/module/iot/api/Greeting.java

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+/*
+ * Copyright (C) 2012-present 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
+ *
+ *     http://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 cn.iocoder.yudao.module.iot.api;
+
+import org.pf4j.ExtensionPoint;
+
+/**
+ * @author Decebal Suiu
+ */
+public interface Greeting extends ExtensionPoint {
+
+    String getGreeting();
+
+}

yudao-module-iot/yudao-module-iot-plugin-api/src/main/java/cn/iocoder/yudao/module/iot/api/package-info.java

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+/**
+ * 占位
+ *
+ * TODO 芋艿：后续删除
+ */
+package cn.iocoder.yudao.module.iot.api;