chore: update GitHub Actions workflow syntax and add checkout_url field to CheckoutSessions model

Author: princemuichkine

.github/workflows/python.yml

@@ -5,7 +5,7 @@
 
 name: lomi Python package
 
-on: [push, pull_request]
+on: [ push, pull_request ]
 
 permissions:
   contents: read
@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+        python-version: [ "3.9", "3.10", "3.11", "3.12", "3.13" ]
 
     steps:
       - uses: actions/checkout@v5

lomi/models/checkout_sessions.py

@@ -9,6 +9,7 @@ class CheckoutSessions(BaseModel):
     amount: float = Field(default=None)
     cancel_url: Optional[str] = Field(default=None)
     checkout_session_id: str = Field(default=None)
+    checkout_url: Optional[str] = Field(default=None)
     created_at: str = Field(default=None)
     created_by: Optional[str] = Field(default=None)
     currency_code: CurrencyCode = Field(default=None)