[BUG][Java][Spring] "gradlew openApiGenerate" does not work well version 5.0.0

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

Hello :)
I could run gradlew openApiMeta but,"gradlew openApiGenerate" don't work well.
Then I checked the command "openApiGenerate" is enable to run "gradlew tasks" and found the command from task lists.
I wonder that is bug.

openapi-generator version

5.0.0
(version 4 work well)

OpenAPI declaration file content or url

build.gradle

buildscript {
    ext {
        springBootVersion = '2.1.5.RELEASE'
    }
    repositories {
        mavenCentral()
        maven {
            url "https://plugins.gradle.org/m2/"
        }
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
        classpath "org.openapitools:openapi-generator-gradle-plugin:5.0.0"
        
    }
}

apply plugin: "org.springframework.boot"
apply plugin: "org.openapi.generator"

dependencies {
    implementation('org.springframework.boot:spring-boot-starter-batch')

    compileOnly('org.projectlombok:lombok:1.18.4')
    annotationProcessor('org.projectlombok:lombok:1.18.4')

    testImplementation('org.springframework.boot:spring-boot-starter-test')
    testImplementation('org.springframework.batch:spring-batch-test')
}

openApiGenerate {
    generatorName = "spring"
    version = "1.0.0"
    inputSpec = "$rootDir/specs/petstore-v3.0.yaml".toString()
    outputDir = "$buildDir/generated".toString()
    invokerPackage = "com.example"
    apiPackage = "com.example.api"
    modelPackage = "com.example.model"
    configOptions = [
        dateLibrary: "java8-localdatetime",
        interfaceOnly: "true"
    ]
    globalProperties = [
        modelDocs: "false"
    ]
}

openApiMeta {
    generatorName = "Sample"
    packageName = "org.openapitools.example"
    outputFolder = "$buildDir/meta".toString()
}

Generation Details

------------------------------------------------------------
Gradle 5.1
------------------------------------------------------------

Build time:   2019-01-02 18:57:47 UTC
Revision:     d09c2e354576ac41078c322815cc6db2b66d976e

Kotlin DSL:   1.1.0
Kotlin:       1.3.11
Groovy:       2.5.4
Ant:          Apache Ant(TM) version 1.9.13 compiled on July 10 2018
JVM:          11.0.2 (Amazon.com Inc. 11.0.

Steps to reproduce

1. write build.gradle
2. run ".\gradlew openApiMeta <- work well
3. run ".\gradlew opemApiGenerate

.\gradlew openApiGenerate

FAILURE: Build failed with an exception.

* What went wrong:
Could not determine the dependencies of task ':openApiGenerate'.
> Cannot resolve object of unknown type String to a Task.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.       

* Get more help at https://help.gradle.org

BUILD FAILED in 1s

I found that from "gradlew tasks"

.\gradlew tasks

------------------------------------------------------------
Tasks runnable from root project
------------------------------------------------------------

Application tasks
-----------------
bootRun - Runs this project as a Spring Boot application.

Build tasks
-----------
assemble - Assembles the outputs of this project.
bootJar - Assembles an executable jar archive containing the main classes and their dependencies.
build - Assembles and tests this project.
buildDependents - Assembles and tests this project and all projects that depend on it.
buildNeeded - Assembles and tests this project and all projects it depends on.
classes - Assembles main classes.
clean - Deletes the build directory.
jar - Assembles a jar archive containing the main classes.
testClasses - Assembles test classes.

Build Setup tasks
-----------------
init - Initializes a new Gradle build.
wrapper - Generates Gradle wrapper files.

Documentation tasks
-------------------
javadoc - Generates Javadoc API documentation for the main source code.

Help tasks
----------
buildEnvironment - Displays all buildscript dependencies declared in root project 'GenerateTemplate'.
components - Displays the components produced by root project 'GenerateTemplate'. [incubating]
dependencies - Displays all dependencies declared in root project 'GenerateTemplate'.
dependencyInsight - Displays the insight into a specific dependency in root project 'GenerateTemplate'.
dependencyManagement - Displays the dependency management declared in root project 'GenerateTemplate'.
dependentComponents - Displays the dependent components of components in root project 'GenerateTemplate'. [incubating]
help - Displays a help message.
model - Displays the configuration model of root project 'GenerateTemplate'. [incubating]
projects - Displays the sub-projects of root project 'GenerateTemplate'.
properties - Displays the properties of root project 'GenerateTemplate'.
tasks - Displays the tasks runnable from root project 'GenerateTemplate'.

OpenAPI Tools tasks
-------------------
openApiGenerate - Generate code via Open API Tools Generator for Open API 2.0 or 3.x specification documents.
openApiGenerators - Lists generators available via Open API Generators.
openApiMeta - Generates a new generator to be consumed via Open API Generator.
openApiValidate - Validates an Open API 2.0 or 3.x specification document.

Verification tasks
------------------
check - Runs all checks.
test - Runs the unit tests.

Rules
-----
Pattern: clean<TaskName>: Cleans the output files of a task.
Pattern: build<ConfigurationName>: Assembles the artifacts of a configuration.
Pattern: upload<ConfigurationName>: Assembles and uploads the artifacts belonging to a configuration.

To see all tasks and more detail, run gradlew tasks --all

To see more detail about a task, run gradlew help --task <task>

Related issues/PRs

Suggest a fix

Start with the supplied build.gradle and reproduce the failure using Gradle 5.1, Java 11, and openapi-generator-gradle-plugin 5.0.0. Compare the working openApiMeta task with openApiGenerate and inspect the reported dependency-resolution error. Done means openApiGenerate runs successfully and generates the configured output from the supplied OpenAPI specification.