#860: remove complete missing periods option from API

Related to dbnomics-fetchers/management#860 (closed)

Depends on other MR: dbnomics-data-model!46 (merged), do not forget updating dependency version.

Description

Describe in one sentence if necessary:

• the implementation details of this MR: call new function dbnomics_data_model.observations.align_series_list, remove series completion

To do before merging

Do the following tasks when relevant, and check the boxes:

• issue URL has been completed (replace TODO by issue number)
• MR description section has been updated (or deleted)
• "next" section of changelog has been updated
• abstract dependency version constraints have been updated in setup.py
• concrete dependency versions have been frozen in requirements.txt (with pip-compile)