WIP: initial feature description for key uploads

This is an initial draft of the keys api for uploading other
keys than the OpenPGP public key.

refers #8815

features/1/keys.feature

+Feature: Handle current users collection of keys
+
+  LEAP currently uses OpenPGP and is working on implementing katzenpost.
+  Both systems require public keys of a user to be available for retrival.
+
+  The /1/keys endpoint allows the client to manage the public keys
+  registered for their users email address.
+
+  You need to specify the type of the key when publishing it. Some
+  keytypes such as 'openpgp' and 'katzenpost_id' will only allow a
+  single key to be published. Others such as 'katzenpost_link' allow
+  multiple keys to be registered at the same time. We deal with this
+  by allowing arbitrary json data to be specified as the value of the
+  key. So katzenpost_link keys can be combined in a json data structure.
+
+  POST request will register a new key. In order to replace an existing
+  key you need to send a PATCH request to /keys/:type including the last
+  revision (rev) of the key. This way we can detect conflicts between
+  concurrend updates.
+
+  Background:
+    Given I authenticated
+    Given I set headers:
+      | Accept       | application/json |
+      | Content-Type | application/json |
+      | Authorization | Token token="MY_AUTH_TOKEN" |
+
+  Scenario: Get initial empty set of keys
+    When I send a GET request to "1/keys"
+    Then the response status should be "200"
+    And the response should be:
+    """
+      {}
+    """
+
+  Scenario: Get all the keys
+    Given I have published a "openpgp" key
+    And I have published "katzenpost_kink" keys
+    When I send a GET request to "1/keys"
+    Then the response status should be "200"
+    And the response should be:
+    """
+    {
+    "openpgp": {
+      "type": "openpgp",
+      "value": "ASDF",
+      "rev": "1234567890"
+      },
+    "katzenpost_link": {
+      "type": "katzenpost_link",
+      "value": {
+        "one": "ASDF",
+        "two": "QWER"
+      },
+      "rev": "1234567890"
+      }
+    }
+    """
+
+  Scenario: Get a single key
+    Given I have published a "openpgp" key
+    When I send a GET request to "1/keys/openpgp"
+    Then the response status should be "200"
+    And the response should be:
+    """
+    "ASDF"
+    """
+
+  Scenario: Get a set of keys for one type
+    Given I have published "katzenpost_link" keys
+    When I send a GET request to "1/keys/katzenpost_link"
+    Then the response status should be "200"
+    And the response should be:
+    """
+      {
+        "one": "ASDF",
+        "two": "QWER"
+      }
+    """
+
+  Scenario: Publish an initial OpenPGP key
+    When I send a POST request to "1/keys" with the following:
+    """
+      {
+      "type": "openpgp",
+      "value": "ASDF"
+      }
+    """
+    Then the response status should be "204"
+
+  Scenario: Do not overwrite an existing key
+    Given I have published a "openpgp" key
+    When I send a POST request to "1/keys" with the following:
+    """
+      {
+      "type": "openpgp",
+      "value": "QWER"
+      }
+    """
+    Then the response status should be "422"
+    And the response should be:
+    """
+      {
+      "error": "key already exists"
+      }
+    """
+
+  Scenario: Updating an existing key require revision
+    Given I have published a "openpgp" key
+    When I send a PATCH request to "1/keys/openpgp" with the following:
+    """
+      {
+      "type": "openpgp",
+      "value": "QWER"
+      }
+    """
+    Then the response status should be "422"
+    And the response should be:
+    """
+      {
+      "error": "no revision specified"
+      }
+    """
+
+  Scenario: Updating an existing key
+    Given I have published a "openpgp" key with revision "1234567890"
+    When I send a PATCH request to "1/keys/openpgp" with the following:
+    """
+      {
+      "type": "openpgp",
+      "value": "QWER",
+      "rev": "1234567890"
+      }
+    """
+    Then the response status should be "204"
+
+  Scenario: Publishing an empty key fails
+    When I send a POST request to "1/keys" with the following:
+    """
+      {}
+    """
+    Then the response status should be "422"
+    And the response should be:
+    """
+      {
+      "error": "key type missing"
+      }
+    """