Migrate project to Gradle

* Upgrade all the dependencies to the latest versions
* Fix some incompatibilities
* Fix some warnings

function/http-request-function/build.gradle

@@ -0,0 +1,5 @@
+dependencies {
+    api 'org.springframework.boot:spring-boot-starter-webflux'
+
+    testImplementation 'com.squareup.okhttp3:mockwebserver'
+}

function/http-request-function/pom.xml

@@ -1,29 +0,0 @@
-<?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>
-
-    <parent>
-        <groupId>org.springframework.cloud.fn</groupId>
-        <artifactId>spring-functions-parent</artifactId>
-        <version>4.0.1-SNAPSHOT</version>
-        <relativePath>../../spring-functions-parent/pom.xml</relativePath>
-    </parent>
-
-    <artifactId>http-request-function</artifactId>
-    <name>http-request-function</name>
-    <description>Spring Native Function for Submitting an HTTP request</description>
-
-    <dependencies>
-        <dependency>
-            <groupId>org.springframework.boot</groupId>
-            <artifactId>spring-boot-starter-webflux</artifactId>
-        </dependency>
-        <dependency>
-            <groupId>com.squareup.okhttp3</groupId>
-            <artifactId>mockwebserver</artifactId>
-            <scope>test</scope>
-        </dependency>
-    </dependencies>
-
-</project>