add case [in]sensitivity tests + add OfficialProvider model

`ci` in this context means "Case Insensitive".
`cs` in this context means "Case Sensitive".

New models created:
    - OfficialProvider
      This was required to write a test for checking that
      OfficialProviders behaves as we expect, which was the starter
      for the original aurblup bug.

New tests created:
    - test_official_provider

Modified tests:
    - test_package_base: add ci test
    - test_package: add ci test
    - test_session: add cs test
    - test_ssh_pub_key: add cs test

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

test/test_package.py

@@ -3,6 +3,8 @@ import pytest
 from sqlalchemy import and_
 from sqlalchemy.exc import IntegrityError
 
+import aurweb.config
+
 from aurweb.db import create, query
 from aurweb.models.account_type import AccountType
 from aurweb.models.package import Package
@@ -55,6 +57,20 @@ def test_package():
     assert record is not None
 
 
+def test_package_ci():
+    """ Test case insensitivity of the database table. """
+    if aurweb.config.get("database", "backend") == "sqlite":
+        return None  # SQLite doesn't seem handle this.
+
+    from aurweb.db import session
+
+    with pytest.raises(IntegrityError):
+        create(Package,
+               PackageBase=pkgbase,
+               Name="Beautiful-Package")
+    session.rollback()
+
+
 def test_package_null_pkgbase_raises_exception():
     from aurweb.db import session