[DRAFT] Implement Ledger/Billboard Django Model System

[Geuthur]

Description

Added

• Added new properties in CharacterOwner and CorporationOwner models to access recent ledger and billboard entries.

Changed

• Introduced new models: CharacterLedgerEntry, CorporationLedgerEntry, CharacterBillboardEntry, CorporationBillboardEntry, and AllianceLedgerEntry.
• Updated CorporationApiEndpoints to utilize new ledger models for processing and storing ledger data.
• Enhanced request info schema to include is_final_data property for determining finality of data.
• Refactored billboard data generation logic to streamline the process and improve performance.
• Updated migrations to create new ledger and billboard entry models in the database.

Removed

• Removed CacheManager and BillboardSystem from CorporationApiEndpoints.
• Removed deprecated cache handling code and replaced it with direct database interactions for ledger entries.

Type of Changes

Please select the type of changes made in this pull request:

• Bug Fix (non-breaking change which fixes an Issue)
• New Feature (non-breaking change)
• Other (please specify):

Checklist

Please ensure the following before submitting your pull request:

• I have read the contributing guidelines.
• My code follows the code style of this project.
• I have performed a self-review of my code.
• I have commented my code where necessary.
• All new and existing tests passed.

[codecov]

Codecov Report

❌ Patch coverage is 51.81159% with 133 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
ledger/api/corporation.py	2.44%	40 Missing ⚠️
ledger/models/ledger.py	77.97%	26 Missing ⚠️
ledger/api/character.py	4.00%	24 Missing ⚠️
ledger/api/alliance.py	4.77%	20 Missing ⚠️
ledger/managers/ledger_manager.py	63.89%	8 Missing and 5 partials ⚠️
ledger/models/corporationaudit.py	58.34%	4 Missing and 1 partial ⚠️
ledger/models/characteraudit.py	55.56%	3 Missing and 1 partial ⚠️
ledger/helpers/billboard.py	83.34%	0 Missing and 1 partial ⚠️

@@            Coverage Diff             @@
##           master     #279      +/-   ##
==========================================
+ Coverage   63.25%   65.43%   +2.19%     
==========================================
  Files          51       52       +1     
  Lines        4271     4379     +108     
  Branches      440      444       +4     
==========================================
+ Hits         2701     2865     +164     
+ Misses       1463     1386      -77     
- Partials      107      128      +21     

Files with missing lines	Coverage Δ
ledger/api/schema.py	91.53% <100.00%> (+0.30%)	⬆️
ledger/managers/corporation_journal_manager.py	76.22% <100.00%> (ø)
ledger/models/__init__.py	100.00% <100.00%> (ø)
ledger/helpers/billboard.py	57.24% <83.34%> (+35.09%)	⬆️
ledger/models/characteraudit.py	85.81% <55.56%> (-1.86%)	⬇️
ledger/models/corporationaudit.py	72.65% <58.34%> (-1.63%)	⬇️
ledger/managers/ledger_manager.py	63.89% <63.89%> (ø)
ledger/api/alliance.py	33.13% <4.77%> (+0.19%)	⬆️
ledger/api/character.py	31.71% <4.00%> (+1.82%)	⬆️
ledger/models/ledger.py	77.97% <77.97%> (ø)
... and 1 more

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