text: /*
  
  WallStreet database should store information about brokers, sales groups and its relations.
  
  Each broker must have a unique username. First and last names are also mandatory.
  
  A sales group is a special group that has its own restrictions. Sale groups are used to organize the work of brokers.
  Each group mush have a unique name, transaction type (string), and max transaction amount (a number). All field are
  mandatory.
  
  A sales group can consists of more than one broker, while each broker can be associated with more than one sale group.
  
    TECH NOTES AND NAMING CONVENTION
  - All tables, columns and constraints are named using "snake case" naming convention
  - All table names must be singular (e.g. "user", not "users")
  - All tables (except link tables) should have an id of type BIGINT, which is a primary key
  - Link tables should have composite primary key, that consists of two other foreign key columns
  - All primary key, foreign key, and unique constraint should be named according to the naming convention.
  - All link tables should have a composite key that consists of two foreign key columns
  
  - All primary keys should be named according to the following rule "PK_table_name"
  - All foreign keys should be named according to the following rule "FK_table_name_reference_table_name"
  - All alternative keys (unique) should be named according to the following rule "UQ_table_name_column_name"
  
  */
  
  -- TODO: write SQL script to create a database tables according to the requirements