Fix _render_string_type signature to accept name, length, collation e…

[ElIsaac]

🐛 Problem

In Firebird 3 (tested with the fdb driver), the original _render_string_type method expected a type_ object with attributes like .length, .charset, and .collation. However, it was being called with plain arguments instead, leading to incorrect SQL type rendering and runtime errors such as:
File "~\Desktop\nexus\venv\Lib\site-packages\sqlalchemy_firebird\base.py", line 436, in _render_string_type
text = text + (length and "(%d)" % length or "")

✅ Solution

• Modified _render_string_type to accept direct parameters: name, length, and collation.
• Removed the dependency on extracting attributes from type_.
• Ensures proper SQL type rendering in environments using Firebird 3.

🔍 Notes

• The fix mirrors the behavior of sqlalchemy.sql.compiler._render_string_type.
• Tested with:
  • sqlalchemy-firebird==2.1
  • fdb driver
• Prevents errors related to incorrect SQL generation for string-based fields.

[fdcastel]

Thank you for your contribution, @ElIsaac.

The issue appears to stem from this commit in SQLAlchemy, which modified the signature of _render_string_type.

In hindsight, it seems this API is less stable than I had initially assumed. To improve code robustness, we should add dedicated functions for each CHAR type instead of relying directly on _render_string_type.

I'm looking into this, now.

[fdcastel]

Superseded by #79. Let's close this one.