refac: GET /v1/auth/registration

features/registration_status_endpoint.feature

@@ -0,0 +1,80 @@
+Feature: The SPA can ask whether registration is currently open, without exposing anything else
+
+  As the maintainer of RenewCMS
+  I want a public, unauthenticated GET endpoint that reports whether registration is open, driven by
+    the exact same rule CreateUserUseCase already enforces on POST /v1/auth/register, and that reveals
+    nothing beyond that single boolean
+  So that the SPA can decide whether to show a registration form before the user submits anything,
+    without a second, drifting copy of the "is registration closed" rule and without leaking how many
+    accounts exist or who they belong to
+
+  Background:
+    Given CreateUserUseCase already has a private registrationClosed() bool method that loops over
+      user.Repository.GetAll() and returns true as soon as any existing user has IsVerified true; this
+      slice exports that same check as a new method on CreateUserUseCase (e.g. IsRegistrationOpen() bool,
+      returning the negation) so it can be called from outside the use case, and CreateUser itself keeps
+      calling it exactly as before
+    And this slice adds GET /v1/auth/registration, handled from the same handler package as
+      POST /v1/auth/register (api/handlers/auth), reusing the same CreateUserUseCase instance the
+      register handler already holds; no new use case, no new domain method beyond the exported check,
+      and no second loop over user.Repository.GetAll anywhere in the handler
+    And GET /v1/auth/registration is mounted in api/router.go's NewAuthRouter at the top level, outside
+      every r.Group: not inside the jwtauth.Verifier/Authenticator group that guards /verify,
+      DELETE /register and /me, and not inside either middleware.NewRateLimiter group that guards /login
+      and /password-reset; no jwt cookie is ever read, parsed or validated for this route
+    And the handler decodes no request body and reads no cookie and no claim; it calls
+      CreateUserUseCase.IsRegistrationOpen(), sets the response header Cache-Control: no-store, and
+      responds 200 with a JSON body containing exactly one field, "open", and nothing else: no user
+      count, no usernames, no emails, no is_verified values
+
+  Scenario: Registration is reported open while no verified account exists
+    Given the user repository is empty
+    When the client sends GET /v1/auth/registration with no jwt cookie
+    Then the response status is 200
+    And the response header Cache-Control is "no-store"
+    And the response body is exactly {"open": true}
+
+  Scenario: Registration is reported open while every existing account is unverified
+    Given the user repository contains a user "alice" with IsVerified false
+    When the client sends GET /v1/auth/registration with no jwt cookie
+    Then the response status is 200
+    And the response body is exactly {"open": true}
+
+  Scenario: Registration is reported closed once a verified account exists
+    Given the user repository contains a user "alice" with IsVerified true
+    When the client sends GET /v1/auth/registration with no jwt cookie
+    Then the response status is 200
+    And the response header Cache-Control is "no-store"
+    And the response body is exactly {"open": false}
+
+  Scenario: An expired, forged, or otherwise invalid jwt cookie makes no difference to the response
+    Given the user repository contains a user "alice" with IsVerified true
+    And the client holds a jwt cookie that is expired, forged, or otherwise invalid and would be
+      rejected by jwtauth.Authenticator on any protected route
+    When the client sends GET /v1/auth/registration with that cookie attached
+    Then the response status is 200
+    And the response body is exactly {"open": false}, the same as a request with no cookie at all
+    And the response does not set or clear any cookie
+    And this proves the route never even attempts to parse or validate the cookie, not merely that a
+      valid one would be ignored
+
+  Scenario: The endpoint reveals nothing beyond the open flag
+    Given the user repository contains three users, two verified and one unverified
+    When the client sends GET /v1/auth/registration
+    Then the response body's only top-level field is "open"
+    And the response body contains none of: a user count, a username, an email, or an is_verified value
+
+  Scenario: The route is never rate-limited, unlike login and password reset
+    Given the user repository is empty
+    When the client sends GET /v1/auth/registration 20 times in immediate succession from the same
+      client
+    Then every response status is 200
+    And none of the responses is 429
+
+  Scenario: The same rule CreateUser enforces is what answers this endpoint
+    Given a user.Repository fake containing one user with IsVerified true
+    And a CreateUserUseCase built directly over that fake, a hasher and a mail.Repository fake
+    When IsRegistrationOpen is called
+    Then it returns false
+    And calling CreateUser on the same use case with a new username/email/password returns
+      user.ErrRegistrationClosed, asserted with errors.Is