feat: dbcontext abstraction via dependency

backend/docs/swagger.yaml

@@ -21,6 +21,16 @@ definitions:
       refresh_token:
         type: string
     type: object
+  models.RegistrationBeginRequest:
+    properties:
+      email:
+        type: string
+      password:
+        description: 'TODO: password checking'
+        type: string
+      username:
+        type: string
+    type: object
 info:
   contact: {}
   description: Easy and feature-rich wishlist.
@@ -97,6 +107,13 @@ paths:
     post:
       consumes:
       - application/json
+      parameters:
+      - description: desc
+        in: body
+        name: request
+        required: true
+        schema:
+          $ref: '#/definitions/models.RegistrationBeginRequest'
       produces:
       - application/json
       responses: {}