Confirm/ensure support of Terraform 0.15

[radeksimko]

Terraform 0.15.0-beta1 was released recently and we need to check whether it is fully compatible with the language server.

TODO

• Reflect any CLI changes (should already be reflected in the latest terraform-exec, but Parse terraform version -json output terraform-exec#13 may need to be looked at)
• Reflect new validation JSON output options terraform-exec#141 - Reflect 0.15 changes in diagnostics output terraform-json#29
• Reflect schema changes Support Terraform 0.15 schema terraform-schema#21
  • NestedType introduced in Mildwonkey/protocolv6 terraform#27699 and Mildwonkey/nested type format terraform#27793
    • add support for attributes with nested types in providers schema terraform#28055
    • Add support for protocol v6 schema changes terraform-json#27 / Reflect v0.15 schema changes terraform-json#28
    • Support attribute nested type terraform-schema#31
  • provider_requirements changes introduced in Provider configuration_aliases and module validation terraform#27739
    • Add support for ObjectExpr expression type hcl-lang#23
    • Add schema for Terraform 0.15 terraform-schema#24
    • Reflect v0.15 configuration_aliases in provider referencing terraform-schema#26
  • terraform language configs: Accept and minimally validate a "language" argument terraform#27941 - Add 0.15 terraform language attribute terraform-schema#29
• Reflect any changes in how Terraform installs and stores modules and plugins in .terraform directory

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.
If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the context necessary to investigate further.