Serialize data to yaml

[ahuang11]

Closes #1448

I may have missed some parts, but now looks like:

ProvidedSource00000 ⦙ products_csv:
  access: SELECT * FROM "products_csv"
  columns:
    product_id:
      enum:
      - P013
      - P009
      - '...'
    product_name:
      enum:
      - Desk Lamp
      - Gaming Chair
      - '...'
    category:
      enum:
      - Furniture
      - Appliances
      - '...'
    brand:
      enum:
      - LightWorks
      - ComfortZone
      - '...'
    supplier_id:
      min: 101
      max: 115
    cost_price:
      min: 13
      max: 1000
    retail_price:
      min: 25
      max: 1300
    stock_quantity:
      min: 15
      max: 200
    weight_kg:
      min: 0.1
      max: 18.5
    dimensions:
      enum:
      - 15x15x40
      - 70x70x120
      - '...'
    rating:
      min: 3.8
      max: 4.7
    review_count:
      min: 123
      max: 2341
    launch_date:
      format: datetime
      min: '2022-10-01T00:00:00'
      max: '2023-05-10T00:00:00'
    discontinued:
      type: bool

[codecov]

Codecov Report

❌ Patch coverage is 6.25000% with 45 lines in your changes missing coverage. Please review.
✅ Project coverage is 47.90%. Comparing base (b4d3677) to head (c7fc2de).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
lumen/ai/schemas.py	2.94%	33 Missing ⚠️
lumen/ai/utils.py	14.28%	12 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1449      +/-   ##
==========================================
+ Coverage   47.83%   47.90%   +0.06%     
==========================================
  Files         122      122              
  Lines       20430    20799     +369     
==========================================
+ Hits         9772     9963     +191     
- Misses      10658    10836     +178     

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