Update default API version to v2, fix v1 tests

[jrhoads]

Purpose

This PR updates the default API version to v2 and fixes tests for the generateaddress endpoint in v1.

Approach

The DEFAULT_VERSION in settings.py was changed from v1 to v2. Additionally, the GenerateAddressViewTestCase in tests_views_v1.py was modified to explicitly call the v1 endpoint by prefixing the URL with /v1/. A stray V1_VERSION constant was also added, although it's not directly used in the diff provided. Finally, the mock for new_geonames in tests_views_v2.py was updated to new_geonames_v2 to align with the v2 context.

Key Modifications

• Changed DEFAULT_VERSION from v1 to v2 in rorapi/settings.py.
• Updated GenerateAddressViewTestCase in rorapi/tests/tests_unit/tests_views_v1.py to use /v1/generateaddress/ for tests.
• Modified the mock for the Geonames function in rorapi/tests/tests_unit/tests_views_v2.py from update_address.new_geonames to update_address.new_geonames_v2.

Important Technical Details

• The switch of the default version means that clients not explicitly specifying a version will now hit the v2 API.
• The generateaddress endpoint in v1 tests now correctly targets the v1 path, ensuring future-proof testing as the API evolves.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

[kaysiz]

LGTM