Fix Golang pattern validation with regex fails on commas #20079

[mlebihan]

In a struct, for a type: string accompanied by a pattern, these generated Go directives are corrected:

json:"creditCard,omitempty" validate:"regexp=^4[0-9]{3}\\s[0-9]{4}\\s[0-9]{4}\\s[0-9]{4}$"` 

Test cases added

18 new regular expressions has been taken for test cases, from an SAP help page.

A go test has been run with various values, and it succeeds except for one test case: windowsAbsolutePath that might encounter a go validator.v2 package internal trouble.

Tests are in modules/openapi-generator/src/test/resources/3_0:
ls modules/openapi-generator/src/test/resources/3_0/issue_20079_*

issue_20079_go_regex_wrongly_translated.yaml

# For testing purpose
issue_20079_api_default_test.go                               # In the sample, replace test/api_default_test.go by this one
issue_20079_matching01.json                                   # Copy these candidates json files along
issue_20079_matching02.json
issue_20079_matching03.json
issue_20079_matching04.json
issue_20079_non_matching01.json
issue_20079_non_matching02.json
issue_20079_non_matching03.json
issue_20079_non_matching04.json

The following command should then show the success:

go mod tidy && go vet ./... && go test ./... -v

Remaining problem

This fix mostly fixes the handling of regular expressions with Go.
But there's still two problems remaining, that will require other issues to be handled 👍

1. For javaComments test case, when it should use the ^/\*.*\*/|//[^\\n]*$ pattern, the org.yaml.snakeyaml.scanner parser that scans the spec file, wrongly tells that \* is an invalid escape code.
   But attempting to enter ^/\\*.*\\*/|//[^\\n]*$ keeps the \\* and generates ^/\\*.*\\*/|//[^\n]*$ instead of the wished ^/\*.*\*/|//[^\n]*$

2. For windowsAbsolutePath test case, Go validator.package v2 doesn't look handling this regexp well, and tell it having a bad parameter.

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[wing328]

thanks for the PR

can you please rebase/merge the latest master, which should have the gradle tests fixed?

[wing328]

cc @antihax (2017/11) @grokify (2018/07) @kemokemo (2018/09) @jirikuncar (2021/01) @ph4r5h4d (2021/04) @lwj5 (2023/04)

[mlebihan]

It should be done, now.

[wing328]

thanks for the PR and adding the tests.

can you please PM me to discuss the integration tests when you've time?

Slack: https://join.slack.com/t/openapi-generator/shared_invite/zt-2wmkn4s8g-n19PJ99Y6Vei74WMUIehQA