fix(deps): update dependency mitol-django-common to v2025.12.23.2

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
mitol-django-common	==2025.8.19 → ==2025.12.23.2

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[renovate]

⚠️ Artifact update problem

Renovate failed to update an artifact related to this branch. You probably do not want to merge this PR as-is.

♻ Renovate will retry this branch, including artifacts, only when one of the following happens:

• any of the package files in this branch needs updating, or
• the branch becomes conflicted, or
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The artifact failure details are included below:

File name: uv.lock

Command failed: uv lock --upgrade-package mitol-django-common
Using CPython 3.13.12
  × No solution found when resolving dependencies:
  ╰─▶ Because your project depends on mitol-django-common==2025.12.23.2 and
      mitol-django-common==2025.12.23.2 depends on pytest>=9,<10, we can
      conclude that your project depends on pytest>=9,<10.
      And because mitxpro:dev depends on pytest>=8.0.0,<9, we can conclude
      that your project and mitxpro:dev are incompatible.
      And because your project requires your project and mitxpro:dev, we can
      conclude that your project's requirements are unsatisfiable.

[sentry]

Bug: The update to mitol-django-common may affect the @single_task decorator, but no tests exist to verify the locking mechanism, creating a risk of data corruption.
_{Severity: MEDIUM}

Suggested Fix

Add integration tests for the Celery tasks that specifically validate the locking behavior of the @single_task decorator. These tests should attempt to run the same task concurrently for the same object and assert that only one task instance acquires the lock and executes. This will verify that the updated dependency has not introduced a regression.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location: pyproject.toml#L41

Potential issue: The update to `mitol-django-common` could introduce breaking changes to
the `@single_task` decorator, which is used to prevent race conditions in four critical
Hubspot synchronization tasks. The current test suite does not verify the decorator's
locking behavior, as this functionality is mocked. If the decorator's implementation has
changed between versions, the existing tests would not detect the regression. This could
lead to concurrent task executions for the same object, potentially causing data
corruption or inconsistencies in Hubspot without any immediate application errors.

_{Did we get this right? 👍 / 👎 to inform future reviews.}

[sentry]

Bug: Updating mitol-django-common may cause runtime errors if functions like usernameify or chunks were removed or changed, as they lack local fallbacks.
_{Severity: MEDIUM}

Suggested Fix

Before merging, verify that the required functions (usernameify, create_user_with_generated_username, chunks) are still present and compatible in the new version of mitol-django-common. Consider refactoring the code to use the local versions of dict_without_keys and now_in_utc to remove unnecessary external dependencies.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location: pyproject.toml#L41

Potential issue: The application relies on functions such as `usernameify`,
`create_user_with_generated_username`, and `chunks` imported from the
`mitol-django-common` library. This pull request updates this dependency to a new
version. If these functions were removed or their signatures changed in the new version,
it would cause runtime failures in critical parts of the application, including user
authentication and background tasks. Additionally, there are inconsistencies where
functions like `dict_without_keys` and `now_in_utc` are imported from this external
library despite having local implementations, creating an unnecessary dependency.