Fix the guides which use `className` when generating the project

Describe the bug When creating a new project with the resteasy-jackson extension, it will create its default classes no matter if I provide a className or not. Also the tests are missing but I assume that this is a result of the extension doing something wrong. Following documentation in the getting started guides right now is not possible if the resteasy-jackson extension is involved in the creation process.

Expected behavior Respect the className definition.

Actual behavior (Part of the reproduce section)

To Reproduce Create a project Note: I added also the Neo4j extension to have something to compare with.

mvn io.quarkus:quarkus-maven-plugin:1.10.3.Final:create \                    
    -DprojectGroupId=com.meistermeier.neo4j \
    -DprojectArtifactId=rest-neo4j-quarkus \
    -DclassName="com.meistermeier.neo4j.MovieResource" \
    -Dextensions="neo4j, resteasy-jackson"

creates

➜  rest-neo4j-quarkus tree
.
├── README.md
├── mvnw
├── mvnw.cmd
├── pom.xml
└── src
    └── main
        ├── docker
        │   ├── Dockerfile.fast-jar
        │   ├── Dockerfile.jvm
        │   └── Dockerfile.native
        ├── java
        │   └── com
        │       └── meistermeier
        │           └── neo4j
        │               └── resteasyjackson
        │                   ├── JacksonResource.java
        │                   └── MyObjectMapperCustomizer.java
        └── resources
            ├── META-INF
            │   └── resources
            │       └── index.html
            └── application.properties

11 directories, 11 files

whereas

mvn io.quarkus:quarkus-maven-plugin:1.10.3.Final:create \
    -DprojectGroupId=com.meistermeier.neo4j \
    -DprojectArtifactId=neo4j-quarkus \ 
    -DclassName="com.meistermeier.neo4j.MovieResource" \
    -Dextensions="neo4j"

creates

.
├── README.md
├── mvnw
├── mvnw.cmd
├── pom.xml
└── src
    ├── main
    │   ├── docker
    │   │   ├── Dockerfile.fast-jar
    │   │   ├── Dockerfile.jvm
    │   │   └── Dockerfile.native
    │   ├── java
    │   │   └── com
    │   │       └── meistermeier
    │   │           └── neo4j
    │   │               └── MovieResource.java
    │   └── resources
    │       ├── META-INF
    │       │   └── resources
    │       │       └── index.html
    │       └── application.properties
    └── test
        └── java
            └── com
                └── meistermeier
                    └── neo4j
                        ├── MovieResourceTest.java
                        └── NativeMovieResourceIT.java

15 directories, 12 files

Adding the extension later with ./mvnw quarkus:add-extension -Dextensions="resteasy-jackson" works fine (maybe obvious but I wanted to mention this)

Environment (please complete the following information):

• Output of java -version: 11 / 15

[ia3andy]

We decided on a fix: https://github.com/quarkusio/quarkus/issues/14391

[ia3andy]

I am hesitating between a few solutions:

1. changing the logic so that when className is used (and spring-web is not selected), we automatically add the resteasy example. It would fix all the guides but would make the behavior inconsistent.
2. updating all the guides which already provide example code in the extension set to be consistent with the new example code
3. having a new --examples=resteasy option to specify the examples to use and udpate all the guides which need it…