Introduce decoupled Code Actions

[radeksimko]

Background

Code Actions make an important part of LSP and we can anticipate many use cases in Terraform: https://github.com/hashicorp/terraform-ls/issues?page=2&q=is%3Aopen+is%3Aissue+label%3AtextDocument%2FcodeAction

Therefore it is important to ensure new ones are easy to implement and existing easy to maintain. This can be achieved through appropriate abstraction layers.

Proposal

• Introduce Code Actions hcl-lang#363
• Ensure DecoderContext gets populated with all []CodeActionImpl
• Update textDocument/codeAction handler to use the new abstraction layers
  

  terraform-ls/internal/langserver/handlers/code_action.go

  Line 16 in f1c5821

  func (svc *service) TextDocumentCodeAction(ctx context.Context, params lsp.CodeActionParams) []lsp.CodeAction {

Implementation Notes

This issue intentionally does not focus on specific code actions, which are filled as separate issues. It is considered a dependency for all of them however. It is assumed that any/all of the linked code actions can be implemented on top of the logic this issue talks about.