[SPRING][maven-plugin] swagger-codegen-maven does not recognise the 'bigDecimalAsString' option when generating server stubs

Description

swagger-codegen-maven lacks 'bigDecimalAsString' option when building Spring server stubs

Swagger-codegen version

2.3.1

Swagger declaration file content or url

<plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>io.swagger</groupId>
                <artifactId>swagger-codegen-maven-plugin</artifactId>
                <version>${swagger-codegen-maven-plugin.version}</version>
                <executions>
                    <execution>
                        <id>agency-api</id>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                        <configuration>
                            <bigDecimalAsString>true</bigDecimalAsString>  <-- not recognised
                            <inputSpec>src/main/resources/api.yaml</inputSpec>
                            <language>spring</language>
                            <library>spring-boot</library>
                            <generateSupportingFiles>false</generateSupportingFiles>
                            <invokerPackage>some.package</invokerPackage>
                            <apiPackage>some.package</apiPackage>
                            <modelPackage>some.package</modelPackage>
                            <configOptions>
                                <bigDecimalAsString>true</bigDecimalAsString>
                                <dateLibrary>java8</dateLibrary>
                                <interfaceOnly>true</interfaceOnly>
                                <java8>true</java8>
                                <useBeanValidation>true</useBeanValidation>
                                <delegatePattern>true</delegatePattern>
                            </configOptions>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

Start by reproducing the issue with the shown swagger-codegen-maven configuration, using src/main/resources/api.yaml and the Spring server-stub generator. Inspect how the Maven plugin passes configuration to the Spring generator and how configOptions are handled. Done means bigDecimalAsString is accepted and affects the generated server stubs.