Simplify the kedro new validation logic

[noklam]

Description

Currently, there are multiple ways to validate the inputs

1. Cookiecutter regex
2. _validate_config_file_inputs (also regex based)
3. _validate_selection inside _parse_add_ons_input

They are only used for path of the flow. There are 4 different way to create a project
a. kedro new - interactive prompt
b. kedro new --addon
c. kedro new --config - take a YAML file
(d). kedro new --starter, for example prompts.yml share the regex_validator for addon and starters.

You can find more details of the flow below.

The problem here is:

• _validate_config_file_inputs is almost exactly the same as prompts.yml, which is only used for (c).
• regex is not flexible, because in some case it is much easier to validate after parsing. i.e. how do you write a regex for 1,2,3,4,5 | none | all | 1-5? It is much easier if you parse it first - then we can check if the selection exist or not
• Hard to maintain, everytime there are changes you need to keep all these logic in sync. We have run into a lot of edge case and https://github.com/kedro-org/kedro/pull/3263/files is a good example. We just want to validate a single input but it requires

In addition, we should also move the logic out to a addon.py, it will be more obvious which logic are shared between "starter" and "addon", right now they are blurred in a single starter.py.

Extra explanation

@AhdraMeraliQB
Hope this has more clarity:
Path 1:
kedro new -> starters.py -> add ons flow with prompts -> cookiecutter validation (regex) [1] -> starters.py -> parse add-ons input[1.5] -> validate_range[1.5] -> validate_selection [2] -> add-ons magic happens
Path 2:
kedro new --config=new_project_config.yml -> starter.py -> check config has necessary prompt info: validate_config_against_prompts [3] -> check inputs in the config file are valid: validate_config_file_inputs [4] -> add ons magic happens
[1] - pre-existing flow, used with new kedro project name
[1.5] - new addition to validate add-ons as regex alone is insufficient
[2] - new addition to validate add-ons as regex alone is insufficient
[3] - preexisting flow
[4] - added recently but necessary with or without add-ons, as all config inputs are subject to some restrictions that were not previously checked and would cause unexpected behaviour (e.g. having special characters in project names)
[4] applies the same regex constraints as [1] as it's a different input path, with a call to [1.5] and [2]

Note: this isn't really pressing at the moment, if we end up expanding the scope of this work we may prioritise this.

Context

Possible Implementation

Possible Alternatives

[AhdraMeraliQB]

@DimedS can we close this after #3429 ?

[DimedS]

@DimedS can we close this after #3429 ?

@AhdraMeraliQB thank you for mention that, looks like we still have some of described problems, regex validation still duplicates in Promps.yml and inside of our codebase. It could be done better I believe, but in my opinion right now it's acceptable. Let's ask @noklam also, it was his ticket.

[noklam]

Closing this as it is already outdated and mostly addressed.