[FastAPI] Refactor db modifications

For SQLAlchemy to automatically understand updates from the
external world, it must use an `autocommit=True` in its session.

This change breaks how we were using commit previously, as
`autocommit=True` causes SQLAlchemy to commit when a
SessionTransaction context hits __exit__.

So, a refactoring was required of our tests: All usage of
any `db.{create,delete}` must be called **within** a
SessionTransaction context, created via new `db.begin()`.

From this point forward, we're going to require:

```
with db.begin():
    db.create(...)
    db.delete(...)
    db.session.delete(object)
```

With this, we now get external DB modifications automatically
without reloading or restarting the FastAPI server, which we
absolutely need for production.

Signed-off-by: Kevin Morris <kevr@0cost.org>

test/test_package_base.py

@@ -4,7 +4,7 @@ from sqlalchemy.exc import IntegrityError
 
 import aurweb.config
 
-from aurweb.db import create, query
+from aurweb import db
 from aurweb.models.account_type import AccountType
 from aurweb.models.package_base import PackageBase
 from aurweb.models.user import User
@@ -19,17 +19,19 @@ def setup():
 
     setup_test_db("Users", "PackageBases")
 
-    account_type = query(AccountType,
-                         AccountType.AccountType == "User").first()
-    user = create(User, Username="test", Email="test@example.org",
-                  RealName="Test User", Passwd="testPassword",
-                  AccountType=account_type)
+    account_type = db.query(AccountType,
+                            AccountType.AccountType == "User").first()
+    with db.begin():
+        user = db.create(User, Username="test", Email="test@example.org",
+                         RealName="Test User", Passwd="testPassword",
+                         AccountType=account_type)
 
 
 def test_package_base():
-    pkgbase = create(PackageBase,
-                     Name="beautiful-package",
-                     Maintainer=user)
+    with db.begin():
+        pkgbase = db.create(PackageBase,
+                            Name="beautiful-package",
+                            Maintainer=user)
     assert pkgbase in user.maintained_bases
 
     assert not pkgbase.OutOfDateTS
@@ -38,7 +40,8 @@ def test_package_base():
 
     # Set Popularity to a string, then get it by attribute to
     # exercise the string -> float conversion path.
-    pkgbase.Popularity = "0.0"
+    with db.begin():
+        pkgbase.Popularity = "0.0"
     assert pkgbase.Popularity == 0.0
 
 
@@ -47,27 +50,28 @@ def test_package_base_ci():
     if aurweb.config.get("database", "backend") == "sqlite":
         return None  # SQLite doesn't seem handle this.
 
-    from aurweb.db import session
-
-    pkgbase = create(PackageBase,
-                     Name="beautiful-package",
-                     Maintainer=user)
+    with db.begin():
+        pkgbase = db.create(PackageBase,
+                            Name="beautiful-package",
+                            Maintainer=user)
     assert bool(pkgbase.ID)
 
     with pytest.raises(IntegrityError):
-        create(PackageBase,
-               Name="Beautiful-Package",
-               Maintainer=user)
-    session.rollback()
+        with db.begin():
+            db.create(PackageBase,
+                      Name="Beautiful-Package",
+                      Maintainer=user)
+    db.rollback()
 
 
 def test_package_base_relationships():
-    pkgbase = create(PackageBase,
-                     Name="beautiful-package",
-                     Flagger=user,
-                     Maintainer=user,
-                     Submitter=user,
-                     Packager=user)
+    with db.begin():
+        pkgbase = db.create(PackageBase,
+                            Name="beautiful-package",
+                            Flagger=user,
+                            Maintainer=user,
+                            Submitter=user,
+                            Packager=user)
     assert pkgbase in user.flagged_bases
     assert pkgbase in user.maintained_bases
     assert pkgbase in user.submitted_bases
@@ -75,8 +79,7 @@ def test_package_base_relationships():
 
 
 def test_package_base_null_name_raises_exception():
-    from aurweb.db import session
-
     with pytest.raises(IntegrityError):
-        create(PackageBase)
-    session.rollback()
+        with db.begin():
+            db.create(PackageBase)
+    db.rollback()