Add a sea-orm.toml file for generating entities

[tqwewe]

It may be nice to have a config file (such as sea-orm.toml) which lets you configure which schemas and tables to generate entities for, and where they should be placed.

For example:

# sea-orm.toml
[config]
output = "./src/models/[db_name]/[schema]"
schemas = [ "auth", "product", "customer" ]

[database]
db_type = "Postgres"
db_host = "0.0.0.0"
db_port = "5432"
db_user = "user"
db_pass = "pass"
db_name = "postgres"

Once configured, you could run sea-orm-cli generate and it would generate the following file structure:

- src
  - models
    - postgres
      - auth
        mod.rs
        customers.rs
        other_table.rs
        
      - product
        mod.rs
        products.rs
        other_table.rs
        
      - customer
        mod.rs
        customers.rs
        other_table.rs

This would be typically useful for projects with multiple schemas, without having to manually run the generate command for each.