[doc] [maven] [build] [infrastructure] swagger-codegen-generators Does not compile with jdk8, Fatal error compiling: invalid flag: --release

Description

See title.

Swagger-codegen-generators version

1.0.40-SNAPSHOT/current

Steps to reproduce

• Jdk 8 (as documented in README)
• and maven compile

should suffice to reproduce:

• $ mvn -v
  Apache Maven 3.9.1 (2e178502fcdbffc201671fb2537d0cb4b4cc58f8)
  Maven home: /usr/local/sdkman/candidates/maven/current
  Java version: 1.8.0_372, vendor: Temurin, runtime: /usr/local/sdkman/candidates/java/8.0.372-tem/jre
  Default locale: en_US, platform encoding: UTF-8
  OS name: "linux", version: "5.15.90.1-microsoft-standard-wsl2", arch: "amd64", family: "unix"
  

• $ git clone git@github.com:swagger-api/swagger-codegen-generators.git
  

• $ mvn clean compile
  

Related issues/PRs

Stackoverflow: Intellij maven project Fatal error compiling: invalid flag: --release

Suggest a fix/enhancement

... elaborating best answer, docs and testing.... :

• Downgrading maven-compiler plugin (to maximum version 3.5.1) seems the only choice to stay "backward compatible"... which raises further issues (maven.compiler.source ...)
• Documenting "Jdk >= 9" (or even 11/17 and upgrading maven-compiler) is the other option.

Please discuss/fix

Start with the README's JDK requirement and the Maven configuration used by mvn clean compile. Reproduce the invalid flag: --release failure on JDK 8, then determine whether the project will retain JDK 8 support or document a newer minimum. Verify the chosen change by rerunning the compile command and checking that the documentation and build behavior agree.