Cherry-pick: MSSQL nvarchar N'...' default value handling (#304)

[GingerAdonis]

Upstream PR

dimitri#304

Summary

Adds proper handling of MSSQL nvarchar default values wrapped in N'...' notation (Unicode string literals). Adds a sql-server-nvarchar-to-text transform function that strips the delimiters.

Files

• src/sources/mssql/mssql-cast-rules.lisp
• src/utils/transforms.lisp

Notes

• +13/-1 lines
• PR is from 2015 — may need rebasing/adaptation
• Priority: Lower — very old, likely stale