Update GEP template with some clarifying sections (#4073)

* Update GEP template with some clarifying sections

* Apply suggestions on GEP template update

Co-authored-by: Nick Young <inocuo@gmail.com>

---------

Co-authored-by: Nick Young <inocuo@gmail.com>

Author: rikatz

geps/gep-696/index.md

@@ -13,16 +13,27 @@
 
 (Primary goals of this proposal.)
 
+## Longer Term Goals (optional)
+
+(goals that are not covered initially on this proposal but may be considered long term)
+
 ## Non-Goals
 
 (What is out of scope for this proposal.)
 
-## Introduction
+## Introduction/Overview
 
 (Can link to external doc -- but we should bias towards copying
 the content into the GEP as online documents are easier to lose
 -- e.g. owner messes up the permissions, accidental deletion)
 
+Write here "What" we want to do. What is the proposal aiming to do?
+
+## Purpose (Why and Who)
+
+Write here "Why" we want to do it. What problems are being solved? What personas are
+the target of this proposal, and why will this proposal will make their lives better?
+
 ## API
 (... details, can point to PR with changes)
 
@@ -32,6 +43,17 @@ the content into the GEP as online documents are easier to lose
 ### Gateway For Mesh (East/West)
 (Include East/West API considerations, examples, and if different - APIs)
 
+## Request flow
+Example on the usage flow of this proposal/enhancement. It is suggested to contain
+at least one manifest as example.
+
+Example of a flow description:
+
+* A client makes a request to https://foo.example.com.
+* DNS resolves the name to a `Gateway` address.
+* The reverse proxy receives the request on a `Listener` and does something with it
+* The reverse proxy passes the request through `XPTORoute` modifying the headers to contain `XYZ`
+
 ## Conformance Details
 
 (from https://github.com/kubernetes-sigs/gateway-api/blob/main/geps/gep-2162/index.md#standardize-features-and-conformance-tests-names)
@@ -60,6 +82,11 @@ In any case, the conformance tests file names should be meaningful and easy to u
 
 (Make sure to also include conformance tests that cover mesh)
 
+When describing the new feature, write down some conformance test scenarios the feature should manage,
+to guarantee that future implementors understand what "Conformance" means and what will be tested.
+
+At least _some_ tests should be added at each phase, starting with Provisional.
+
 ## Alternatives
 
 (List other design alternatives and why we did not go in that