refactor: updated swagger;

feat: helper function in errors for checking postgres error types;
feat: sql query method for finding users by their email;
feat: registration begin/complete with checking existing username/email;
refactor: error handling in controller

backend/docs/swagger.yaml

@@ -8,10 +8,13 @@ definitions:
   models.LoginRequest:
     properties:
       password:
+        maxLength: 100
         type: string
       totp:
         type: string
       username:
+        maxLength: 20
+        minLength: 3
         type: string
     required:
     - password
@@ -39,11 +42,39 @@ definitions:
     - password
     - username
     type: object
+  models.RegistrationCompleteRequest:
+    properties:
+      avatar_url:
+        maxLength: 255
+        type: string
+      birthday:
+        type: string
+      name:
+        maxLength: 75
+        type: string
+      username:
+        maxLength: 20
+        minLength: 3
+        type: string
+      verification_code:
+        type: string
+    required:
+    - name
+    - username
+    - verification_code
+    type: object
+  models.RegistrationCompleteResponse:
+    properties:
+      access_token:
+        type: string
+      refresh_token:
+        type: string
+    type: object
 info:
   contact: {}
   description: Easy and feature-rich wishlist.
   license:
-    name: GPL 3.0
+    name: GPL-3.0
   title: Easywish client API
   version: "1.0"
 paths:
@@ -124,7 +155,9 @@ paths:
           $ref: '#/definitions/models.RegistrationBeginRequest'
       produces:
       - application/json
-      responses: {}
+      responses:
+        "200":
+          description: desc
       summary: Register an account
       tags:
       - Auth
@@ -132,9 +165,20 @@ paths:
     post:
       consumes:
       - application/json
+      parameters:
+      - description: desc
+        in: body
+        name: request
+        required: true
+        schema:
+          $ref: '#/definitions/models.RegistrationCompleteRequest'
       produces:
       - application/json
-      responses: {}
+      responses:
+        "200":
+          description: desc
+          schema:
+            $ref: '#/definitions/models.RegistrationCompleteResponse'
       summary: Confirm with code, finish creating the account
       tags:
       - Auth