Keep user data

[glass-ships]

Short description of the changes:

This PR serves to modify the previously added code to preserve user-associated plots while only purging beamline data.

Long description of the changes:

• Allow expiration_date to be blank/null at first
• Move the value assignment for expiration_date into datarun.clean(), allowing the value to be set relative to creation date
• modify migration in a similar way (also merge id data field migration into initial)

Check list for the pull request

• I have read the [CONTRIBUTING]
• I have read the [CODE_OF_CONDUCT]
• I have added tests for my changes
• I have updated the documentation accordingly

Check list for the reviewer

• I have read the [CONTRIBUTING]
• I have verified the proposed changes
• best software practices
  • all internal functions have an underbar, as is python standard
  • clearly named variables (better to be verbose in variable names)
  • code comments explaining the intent of code blocks
• All the tests are passing
• The documentation is up to date
• code comments added when explaining intent

Manual test for the reviewer

References

[codecov]

Codecov Report

Attention: Patch coverage is 89.13043% with 5 lines in your changes missing coverage. Please review.

Project coverage is 89.85%. Comparing base (749e772) to head (05f1dd5).
Report is 14 commits behind head on next.

Files with missing lines	Patch %	Lines
src/apps/plots/models.py	42.85%	4 Missing ⚠️
src/config/instruments.py	97.43%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             next      #37      +/-   ##
==========================================
- Coverage   90.00%   89.85%   -0.15%     
==========================================
  Files          10       11       +1     
  Lines         310      355      +45     
==========================================
+ Hits          279      319      +40     
- Misses         31       36       +5     

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[backmari]

Good catch to not delete user data. The plots created in the unit tests are created correctly with the user data having an expiration date in 2100 and the instrument data three years into the future. Looks good to me 👌

livedatadb=# select * from plots_datarun;
 id | run_number |      run_id       |          created_on           | instrument_id |        expiration_date        
----+------------+-------------------+-------------------------------+---------------+-------------------------------
  5 |      12345 |                   | 2024-09-18 16:32:19.854356+00 |             5 | 2027-09-18 16:32:19.84804+00
  6 |          6 | reflectivity.json | 2024-09-18 16:32:20.024337+00 |             6 | 2100-01-01 00:00:00+00
  7 |      12346 |                   | 2024-09-18 16:32:20.51581+00  |             7 | 2027-09-18 16:32:20.512165+00
  8 |        123 |                   | 2024-09-18 16:32:20.862616+00 |             8 | 2027-09-18 16:32:20.858818+00
(4 rows)