Use Psycopg3 instead of Psycopg2 (#21)

* adjust dependency psycopg2->psycopg[binary]

* require postgresql+psycopg:// in dsn

* replace old dsn prefix to keep .toml backwards compatibility

* update docs

doc/source/configuration.rst

@@ -44,7 +44,7 @@ By default, an SQLite database will be created. If you want to add an existing d
 
 .. code-block::
     
-    ixmp4 platforms add <database-name> --dsn postgresql://user:pw@host/db    
+    ixmp4 platforms add <database-name> --dsn postgresql+psycopg://user:pw@host/db    
 
 From a Python environment, you can then access this **ixmp4 database** using the
 following code:

ixmp4/cli/platforms.py

@@ -26,7 +26,7 @@ def validate_name(name: str):
 def validate_dsn(dsn: str | None):
     if dsn is None:
         return None
-    match = re.match(r"^(sqlite|postgresql|https|http)(\:\/\/)", dsn)
+    match = re.match(r"^(sqlite|postgresql\+psycopg|https|http)(\:\/\/)", dsn)
     if match is None:
         raise typer.BadParameter(
             "Platform dsn must be a valid URl or database connection string."

ixmp4/data/backend/db.py

@@ -48,6 +48,11 @@ def __init__(self, info: PlatformInfo) -> None:
         self.make_repositories()
 
     def make_engine(self, dsn: str):
+        if dsn.startswith("postgresql://"):
+            logger.debug(
+                "Replacing the platform dsn prefix to use the new `psycopg` driver."
+            )
+            dsn = dsn.replace("postgresql://", "postgresql+psycopg://")
         self.engine = cached_create_engine(dsn)
         self.session = self.Session(bind=self.engine)