Fixed-issue-6573-Include examples of implicit request in documentation

[Shruti9520]

Fixes issue playframework/playframework#6573.

[richdougherty]

Hi @Shruti9520, thanks for looking at this!

I have a couple of suggestions:

1. Maybe a good place to mention these implicits is at the end of the Template parameters section of the docs, just before the Template constructor heading.

2. Instead of saying that an implicit Request is required, I think we could tell users that it's useful for CSRF and form helpers and include links to the documentation.

E.g.

You can define implicit parameters for a template too:

@(user: models.User)(implicit requestHeader: RequestHeader, messagesProvider: MessagesProvider)

Many template helpers expect an implicit value to be in scope. For example, Cross-Site Request Forgery (CSRF) protection [needs a RequestHeader](ScalaCsrf#Defining-an-implicit-Requests-in-Templates) and Form Helpers [need a MessageProvider](ScalaForms#Passing-MessagesProvider-to-Form-Helpers).

[Shruti9520]

Hi, @richdougherty

Updated my commit.
Thanks for reviewing. :)

[Shruti9520]

@richdougherty Hi,

I think ScalaCsrf#Defining-an-implicit-Requests-in-Templates is a kind of an external link. Can I use standard Markdown link syntax here?

Thanks!

[gmethvin]

I don't think this example belongs here. This is the Java documentation and you're referencing Scala API classes from Play.

[Shruti9520]

I'll remove this. But I am not sure which example is correct for Java documentation.

[gmethvin]

This is also referencing the scala documentation.