Prefix function names with spring-

* Add `spring-` prefix to function names

Fixes: #9

This commit renames each sub-module in the common, consumer, function
and supplier groups with a prefix of `spring-`.

* Update README.adoc links to new prefixed names

function/spring-spel-function/src/main/java/org/springframework/cloud/fn/spel/SpelFunctionConfiguration.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2020-2020 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.cloud.fn.spel;
+
+import java.util.function.Function;
+
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.expression.spel.standard.SpelExpressionParser;
+import org.springframework.integration.transformer.ExpressionEvaluatingTransformer;
+import org.springframework.messaging.Message;
+
+@Configuration
+@EnableConfigurationProperties(SpelFunctionProperties.class)
+public class SpelFunctionConfiguration {
+
+	@Bean
+	public Function<Message<?>, Message<?>> spelFunction(
+			ExpressionEvaluatingTransformer expressionEvaluatingTransformer) {
+
+		return message -> expressionEvaluatingTransformer.transform(message);
+	}
+
+	@Bean
+	public ExpressionEvaluatingTransformer expressionEvaluatingTransformer(
+			SpelFunctionProperties spelFunctionProperties) {
+
+		return new ExpressionEvaluatingTransformer(new SpelExpressionParser()
+				.parseExpression(spelFunctionProperties.getExpression()));
+	}
+
+}

function/spring-spel-function/src/main/java/org/springframework/cloud/fn/spel/SpelFunctionProperties.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2020-2020 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.cloud.fn.spel;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.expression.Expression;
+import org.springframework.expression.spel.standard.SpelExpressionParser;
+
+/**
+ * Configuration properties for the SpEL function.
+ *
+ * @author Gary Russell
+ * @author Artem Bilan
+ */
+@ConfigurationProperties("spel.function")
+public class SpelFunctionProperties {
+
+	private static final Expression DEFAULT_EXPRESSION = new SpelExpressionParser().parseExpression("payload");
+
+	/**
+	 * A SpEL expression to apply.
+	 */
+	private String expression = DEFAULT_EXPRESSION.getExpressionString();
+
+	public String getExpression() {
+		return this.expression;
+	}
+
+	public void setExpression(String expression) {
+		this.expression = expression;
+	}
+
+}

function/spring-spel-function/src/main/resources/META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports

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+org.springframework.cloud.fn.spel.SpelFunctionConfiguration