added SQL query generator: Classes, Properties, Associations (Binary + N-ary)

[FChikh]

BUML -> SQL converter Generates SQL query from Jinja template; available for conversion - Classes, Properties, Associations; coming - Generalizations. I also implemented GeneratorInterface to access the generator.

[jcabot]

The indentation of the jinja commands doesn't seem right (all seem to be on the same position even for instructions within a loop or conditional)

Also, this is not a SQL generator, it is a Postgresql generator.

You could probably refactor the code to have a common part as a SQLGenerator (at least the structure of going through the classes, ends,...) and then a specific part where we use the specific types and syntax of postrgresql

[ivan-alfonso]

I would suggest avoiding relative imports and using absolute imports. PEP 8 (Style Guide for Python Code) explicitly recommends absolute imports because they are usually more readable and tend to be better behaved.

We have currently the src/ directory, then the following import:

from ...BUML.metamodel.structural.structural import DomainModel

could be replaced by this:

from BUML.metamodel.structural.structural import DomainModel

[ivan-alfonso]

The indentation of the jinja commands doesn't seem right (all seem to be on the same position even for instructions within a loop or conditional)

The following could be a solution to address indentation in Jinja templates and improve readability

https://ttl255.com/jinja2-tutorial-part-3-whitespace-control/#block-ind

[FChikh]

1) Fixed indentation, thank you for resources

2) Added a separate file sql_dialects.sql.j2, where I put parts of pure SQL code, with the option of choosing a dialect (PostgreSQL and MySQL are available for now, as a demonstration)