Add dynamic header injection based on request path

[Copilot]

Adds support for conditionally setting request headers based on URL path matching via a new add_header_based_on_path variable.

Changes

• modules/service-vcl/variables.tf — New add_header_based_on_path variable: list(object({ path, header_name, header_value }))
• modules/service-vcl/vcl-service.tf — Two new dynamic blocks:
  • dynamic "condition" — generates a REQUEST condition per entry matching req.url.path
  • dynamic "header" — sets the named header to the specified value, gated by the corresponding path condition
• prod-delivery/variables.tf — Mirrors the same variable declaration
• prod-delivery/main.tf — Passes add_header_based_on_path through to the module

Example

add_header_based_on_path = [
  { path = "/anything/foo",     header_name = "foo",     header_value = "a" },
  { path = "/anything/bar",     header_name = "bar",     header_value = "b" },
  { path = "/anything/charlie", header_name = "charlie", header_value = "c" },
]

Condition and header action names are derived from the path (e.g., /anything/foo → path-condition-anything-foo, header-foo-anything-foo) to ensure uniqueness across entries.