Add support for the GitCredentialID in the portainer_stack

[HellsCrimson]

Is your feature request related to a problem? Please describe

When adding a lot of stacks (or migrating them in my case) the stacks uses a common GitCredentialID in order to not redefine each time the configuration for the private git repository (url, username, token).

Describe the solution you'd like

I would like to have the ability to set the GitCredentialID so that the other git config is not necessary to set

Describe alternatives you've considered

As in the ui the GitCredentialID is linked to the user, it may be necessary to limit the id to the user used for the terraform.

Additional context

The example from the current api used by the frontend is like this:

"GitConfig": {
    "URL": "<url>",
    "ReferenceName": "refs/heads/main",
    "ConfigFilePath": "<path>",
    "Authentication": {
        "Username": "",
        "Password": "",
        "AuthorizationType": 0,
        "GitCredentialID": <the-id>
    },
    "ConfigHash": "<hash>",
    "TLSSkipVerify": false
},

The url, reference name, config path, tls skip verify being already implemented, this would be the last element to add

[grulicht]

Hi @HellsCrimson ,
thanks a lot for using the Portainer Terraform provider and for taking the time to report this issue – your detailed reproduction and example repo are super helpful! 🙌

We're investigating the root cause and will include a fix in one of the upcoming releases. We'll make sure to notify you once it's available. 🚀

[grulicht]

Hi @HellsCrimson ,
New release version v1.21.0 with patch is out! 🙌🏽