Feat: Add subnet to a existing virtual network

[herms14]

Fixed telemetry variable and added feature to attach a subnet to a existing Virtual network

Description

Type of Change

• [ ] Non-module change (e.g. CI/CD, documentation, etc.)
• [ ] Azure Verified Module updates:
  • [ ] Bugfix containing backwards compatible bug fixes, and I have NOT bumped the MAJOR or MINOR version in locals.version.tf.json:
  • [X] Someone has opened a bug report issue. Close #61 and #43
  • [ ] The bug was found by the module author, and no one has opened an issue to report it yet.
  • [ ] Feature update backwards compatible feature updates, and I have bumped the MINOR version in locals.version.tf.json.
  • [ ] Breaking changes and I have bumped the MAJOR version in locals.version.tf.json.
  • [X] Update to documentation

Checklist

• [x] I'm sure there are no other open Pull Requests for the same update/change
• [x] My corresponding pipelines / checks run clean and green without any errors or warnings
• [x] I did run all pre-commit checks

[matt-FFFFFF]

Great work!

A few comments for consideration.

• adding a moved block
• adding more locals to determine the vnet details. These locals would provide the values for either the existing or the new vnet, depending on whether the existing input is null.

Coalesce is a good function to use here!

[herms14]

thanks for the feedback guys. been busy with other stuffs lately so will be able to woro on these change probably by next week

[kewalaka]

i've got a potentially better way to do this, which also address #71

currently testing it here; https://github.com/kewalaka/terraform-azurerm-avm-res-network-virtualnetwork/tree/feat/use-azapi-for-subnets

[kewalaka]

74 supersedes this and addresses some other issues as noted in that PR.

[matt-FFFFFF]

Closing in favour of #74