Provide a consistent developer experience for all function templates

[omerbensaadon]

Context

During the user interviews, we noticed there is a lot of variance between the templates of each language, and there are some issues with the templates as a whole. Namely, we need to...

• Effectively highlight where the developer inserts their code (//CAN'T MISS COMMENT + Method at the top)
• Make sure the code is effectively commented to assist in developer's understanding of said code
• Make sure the template returns some value ("Hello World!" + message payload) when it is pinged

---

Story

As Deandra the Developer
I want to better understand how func templates work
So that I can better leverage the templates for my personal needs

Acceptance Criteria

• Effectively highlight where the developer inserts their code, where the code handles incoming data

GIVEN I have created a new func project 
WHEN I inspect the "main" file (func.py. index.js, handler.go) 
THEN I see that the method for handling incoming data is listed as the first method 
AND THEN I see a comment within the method which makes it clear where I would put my business logic

• Go
• Node.js
• Python
• Quarkus
• Rust
• Springboot
• TypeScript

The comment within the method should be something to the effect of: //YOUR CODE GOES HERE

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• Make sure code is effectively commented to assist in developer's understanding

GIVEN I have created a new func project 
WHEN I inspect the "main" file (func.py. index.js, handler.go) 
THEN I see that each method within the "main" file is effectively commented
AND THEN I see that each line is commented with an explanation of what that line does

• Go
• Node.js
• Python
• Quarkus
• Rust
• Springboot
• TypeScript

---

• Make sure the templates return similar data when invoked

GIVEN I have created a new func project 
AND GIVEN I have built and am currently running the project without any changes
WHEN I invoke the endpoint where the function is running locally using `func invoke`
THEN I see that the currently running function has returned the raw data which was sent to it

AND THEN on a new line, I see that the method returns "Hello from func!"
(Removed from acceptance criteria)

• Go
• Node.js
• Python
• Quarkus
• Rust
• Springboot
• TypeScript

---

• All templates come out of the box with unit tests

GIVEN I have created a new func project
WHEN I use tools appropriate for the runtime to run tests on a project
THEN I can successfully execute unit tests on my function

• Go
• Node.js
• Python
• Quarkus
• Rust
• Springboot
• TypeScript

[github-actions]

This issue is stale because it has been open for 90 days with no
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[zroubalik]

/remove-lifecycle stale

[lance]

Consider as inspiration https://github.com/GoogleCloudPlatform/functions-framework

[lkingland]

An example of this "Default Template which all languages must follow" was create in Go in #741. This may serve as a starting-point for other builtin language templates.

In particular, 1) there is a large "YOUR CODE HERE" in the Function's function block, 2) extra commentary is below the function such that the most important part is at the top (their new function and the aforementioned callout), and 3) the default function implementation is the absolute minimum necessary to work out-of-the-box and provide end-to-end verification: an echo of input received*.

• currently only the http template echoes. We are discussing perhaps updating the CloudEvents template such that it also echos, with the tradeoff being added complexity and an extra dependency.