Some refactor. Some docstrings.

db/create.py

@@ -1,5 +1,46 @@
+"""
+Create database file and tables if not exists.
+::
+
+    +--------------+
+    |services      |                 +---------------+
+    +--------------+                 |notifications  |
+    |service_id    |<--------+       +---------------+
+    |token         |         |       |notification_id|
+    |name          |         +-------|service_id     |
+    |description   |                 |timestamp      |
+    |representation|                 |content_json   |
+    |by_request    |                 +---------------+
+    +--------------+
+
+* services table
+    * **service_id:**      service id
+                               *(integer primary key)*.
+    * **token:**           service token for access to api
+                               *(text, not null)*.
+    * **name:**            service name
+                               *(text, not null)*.
+    * **description:**     service description
+                               *(text with default value)*.
+    * **representation:**  how to display notification
+                               *(integer with 0 as default)*.
+    * **by_request:**      send notifications automatically or not
+                               *(integer with 0 as default)*.
+* notifications table
+    * **notification_id:** notification id
+                               *(integer primary key)*.
+    * **service_id:**      service id
+                               *(integer, not null, references to*
+                               *service_id in service table)*.
+    * **timestamp:**       UTC timestamp, example: **"2022-02-14T13:45:15Z"**
+                               *(text, not null)*.
+
+    * **content_json:**    content in json_format
+                               *(text, not null)*.
+"""
 import sqlite3
 
+
 CREATE_SERVICES_TABLE = '''CREATE TABLE IF NOT EXISTS services (
 service_id INTEGER PRIMARY KEY,
 token TEXT NOT NULL,
@@ -20,6 +61,12 @@ ON UPDATE CASCADE ON DELETE CASCADE
 
 
 def create_tables_if_not_exists(dbfile: str) -> None:
+    """
+    Create database file and tables if not exists.
+    *See module docstring*.
+
+    :param dbfile: path to database file.
+    """
     connection = sqlite3.connect(dbfile)
     cursor = connection.cursor()
     cursor.execute('PRAGMA foreign_keys=0')