[gradle] consistent use of maven url in gradle files

[sebastien-rosset]

According to https://docs.gradle.org/current/userguide/declaring_repositories.html, the syntax for maven repositories is:

repositories {
    maven {
        url "https://maven.springframework.org/release"
    }
}

There is no equal sign between the 'url' keyword and the value.

PR checklist

• Read the contribution guidelines.
• If contributing template-only or documentation-only changes which will change sample output, build the project before.
• Run the shell script(s) under ./bin/ (or Windows batch scripts under.\bin\windows) to update Petstore samples related to your fix. This is important, as CI jobs will verify all generator outputs of your HEAD commit, and these must match the expectations made by your contribution. You only need to run ./bin/{LANG}-petstore.sh, ./bin/openapi3/{LANG}-petstore.sh if updating the code or mustache templates for a language ({LANG}) (e.g. php, ruby, python, etc).
• File the PR against the correct branch: master, 4.3.x, 5.0.x. Default: master.
• Copy the technical committee to review the pull request if your PR is targeting a particular programming language.

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[jimschubert]

LGTM

[jimschubert]

I did some investigation into why both of these work (with and without the equals).

All of these appear to be the same in build.gradle:

maven { url "https://repo1.maven.org/maven2" }
maven { url("https://repo1.maven.org/maven2") }
maven { url = "https://repo1.maven.org/maven2" }

But, I'm not sure of what the underlying Groovy support is that enables this. See the below example where I have a property and a setter.

groovy:000> class Example {
groovy:001>     def url
groovy:002>     void setUrl(Object url) {
groovy:003>         this.url = url
groovy:004>     }
groovy:005>
groovy:005>     String toString() {
groovy:006>         return "Example: $url"
groovy:007>     }
groovy:008> }
===> true
groovy:000> example = new Example()
===> Example: null
groovy:000> example.url = "http://direct.example.com"
===> http://direct.example.com
groovy:000> example.setUrl("http://setter.example.com")
===> null
groovy:000> println example.toString()
Example: http://setter.example.com
===> null
groovy:000> example.url "http://sugared.example.com"
ERROR groovy.lang.MissingMethodException:
No signature of method: Example.url() is applicable for argument types: (String) values: [http://sugared.example.com]
Possible solutions: use([Ljava.lang.Object;), any(), dump(), grep(), getUrl(), use(java.lang.Class, groovy.lang.Closure)

It probably has something to do with the Closure. Anyway, best to stick with idiomatic Gradle and not use something which could potentially break in the future. Thanks for fixing it up!