Remove opinion on Netty from core module

Currently the spring-grpc-core imposes an opinion on Netty.
The core module should not have an opinion, but rather the
starter enforces the opinion.

Also, makes spring-grpc-core optional in the autconfigure
module as the autoconfigure will eventually be moved into
Spring Boot and at that time everything is optional.

Signed-off-by: Chris Bono <chris.bono@gmail.com>

samples/grpc-server-netty-shaded/build.gradle

@@ -29,14 +29,11 @@ dependencyManagement {
 }
 
 dependencies {
-    implementation 'org.springframework.grpc:spring-grpc-spring-boot-starter'
+    implementation ('org.springframework.grpc:spring-grpc-spring-boot-starter') {
+		exclude group: "io.grpc", module: "grpc-netty"
+	}
     implementation 'io.grpc:grpc-netty-shaded'
     implementation 'io.grpc:grpc-services'
-    modules {
-        module("io.grpc:grpc-netty") {
-            replacedBy("io.grpc:grpc-netty-shaded", "Use Netty shaded instead of regular Netty")
-        }
-    }
     testImplementation 'org.springframework.boot:spring-boot-starter-test'
     testImplementation 'org.springframework.grpc:spring-grpc-test'
     testRuntimeOnly 'org.junit.platform:junit-platform-launcher'

spring-grpc-core/pom.xml

@@ -54,6 +54,7 @@
 		<dependency>
 			<groupId>io.grpc</groupId>
 			<artifactId>grpc-netty</artifactId>
+            <optional>true</optional>
 		</dependency>
 		<dependency>
 			<groupId>io.grpc</groupId>

spring-grpc-spring-boot-autoconfigure/pom.xml

@@ -51,6 +51,7 @@
 			<groupId>org.springframework.grpc</groupId>
 			<artifactId>spring-grpc-core</artifactId>
 			<version>${project.version}</version>
+            <optional>true</optional>
 		</dependency>
 		<dependency>
 			<groupId>org.springframework</groupId>
@@ -72,6 +73,11 @@
 			<artifactId>grpc-services</artifactId>
 			<optional>true</optional>
 		</dependency>
+        <dependency>
+            <groupId>io.grpc</groupId>
+            <artifactId>grpc-netty</artifactId>
+            <optional>true</optional>
+        </dependency>
 		<dependency>
 			<groupId>io.grpc</groupId>
 			<artifactId>grpc-netty-shaded</artifactId>

spring-grpc-spring-boot-starter/pom.xml

@@ -24,6 +24,10 @@
 			<artifactId>spring-grpc-spring-boot-autoconfigure</artifactId>
 			<version>${project.version}</version>
 		</dependency>
+        <dependency>
+            <groupId>io.grpc</groupId>
+            <artifactId>grpc-netty</artifactId>
+        </dependency>
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter</artifactId>

spring-grpc-test/pom.xml

@@ -25,6 +25,11 @@
 	</properties>
 
 	<dependencies>
+        <dependency>
+            <groupId>org.springframework.grpc</groupId>
+            <artifactId>spring-grpc-core</artifactId>
+            <version>${project.version}</version>
+        </dependency>
 		<dependency>
 			<groupId>org.springframework.grpc</groupId>
 			<artifactId>spring-grpc-spring-boot-autoconfigure</artifactId>
@@ -39,6 +44,11 @@
 			<groupId>io.grpc</groupId>
 			<artifactId>grpc-testing</artifactId>
 		</dependency>
+        <dependency>
+            <groupId>io.grpc</groupId>
+            <artifactId>grpc-netty</artifactId>
+            <optional>true</optional>
+        </dependency>
 		<dependency>
 			<groupId>io.grpc</groupId>
 			<artifactId>grpc-inprocess</artifactId>