feat(google-drive): support key-value template replacements

[azan-baloch]

Description

Added a new key-value template replacement mode for the Google Drive connector.

Previously, users had to provide full Google Docs API request syntax even for basic placeholder replacements.

Example:

{
  "requests": [
    {
      "replaceAllText": {
        "containsText": {
          "text": "{{candidateName}}",
          "matchCase": true
        },
        "replaceText": candidateName
      }
    },
    {
      "replaceAllText": {
        "containsText": {
          "text": "{{jobTitle}}",
          "matchCase": true
        },
        "replaceText": jobTitle
      }
    }
  ]
}

With this change, users can now use a simpler key-value format for common template replacement workflows:

{
  "candidateName": "Azan Baloch",
  "jobTitle": "Junior Developer",
  "salary": "$2000"
}

The connector internally converts these key-value pairs into Google Docs replace requests.

This PR also keeps backward compatibility with the existing advanced Google Docs request format.

Demo

The video below shows the new key-value template replacement mode working in a local Docker setup.

Related issues

closes #7335

Checklist

• Backport labels are added if these code changes should be backported. No backport label is added to the latest
  release, as this branch will be rebased onto main before the next release. Example backport labels:
  • backport stable/8.8: for changes that should be included in the next 8.8.x release.
  • or backport release-8.8.7: for changes that should be included in the specific release 8.8.7, and this
    release has already been created. The release branch will be merged back into stable/8.8 later, so the change
    will be included in future 8.8.x releases as well.
• Tests/Integration tests for the changes have been added if applicable.
• If the change requires a documentation update, it has been added to the appropriate section in the documentation.

[CLAassistant]

All committers have signed the CLA.

[mathias-vandaele]

I am a bit hesitant with this approach.

Today the connector is basically centered around the native Google Docs request format, and the runtime still consumes template.variables.requests and forwards that to the Docs batch update API. With this PR we introduce an additional key-value replacement format via a new mapping in the element template.

My concern is that this adds a second mapping system that we now need to own and support on our side, instead of staying with the Google-native format.

What do you think @crobbins215 @sbuettner ?