Add OpenTofu module for GitHub repo guard-rails

Manages branch protection ruleset and deployment environments for this
repository. Mirrored to JMR-dev/gh-repo-bootstrap as a reusable module
+ gh CLI extension.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

infra/github/variables.tf

@@ -0,0 +1,39 @@
+variable "repo_owner" {
+  description = "GitHub user or organization that owns the repository."
+  type        = string
+}
+
+variable "repo_name" {
+  description = "Repository name (without owner prefix)."
+  type        = string
+}
+
+variable "default_branch" {
+  description = "Branch protected by the ruleset."
+  type        = string
+  default     = "main"
+}
+
+variable "required_reviews" {
+  description = "Number of required approving reviews on PRs targeting the default branch."
+  type        = number
+  default     = 1
+}
+
+variable "require_signed_commits" {
+  description = "Require signed commits on the protected branch."
+  type        = bool
+  default     = false
+}
+
+variable "environments" {
+  description = "List of GitHub deployment environments to ensure exist."
+  type        = list(string)
+  default     = []
+}
+
+variable "ruleset_name" {
+  description = "Name to give the branch protection ruleset."
+  type        = string
+  default     = "default-branch-protection"
+}