Rename Flex::Rules to Strata namespace (#197)

## Changes

Renamed the `Flex::Rules` module namespace to `Strata` by moving 4 files
and updating module declarations:

- **Moved files:**
- `app/models/flex/rules/medicaid_ruleset.rb` →
`app/models/strata/medicaid_ruleset.rb`
- `app/models/flex/rules/paid_leave_ruleset.rb` →
`app/models/strata/paid_leave_ruleset.rb`
- `spec/models/flex/rules/medicaid_ruleset_spec.rb` →
`spec/models/strata/medicaid_ruleset_spec.rb`
- `spec/models/flex/rules/paid_leave_ruleset_spec.rb` →
`spec/models/strata/paid_leave_ruleset_spec.rb`

- **Updated module declarations:** Changed from `module Flex::Rules` to
`module Strata`
- **Removed empty directories:** `app/models/flex/rules/` and
`spec/models/flex/rules/`

The classes are now accessible as `Strata::MedicaidRuleset` and
`Strata::PaidLeaveRuleset` instead of `Flex::Rules::MedicaidRuleset` and
`Flex::Rules::PaidLeaveRuleset`.

## Context

This refactoring integrates the ruleset classes into the existing Strata
namespace, which already contains models, controllers, attributes, and
other components throughout the codebase. The target structure is flat
(`Strata::MedicaidRuleset`) rather than nested
(`Strata::Rules::MedicaidRuleset`).

**⚠️ Breaking Change:** This is a breaking change for any code that
references these classes by their old namespace. A comprehensive search
found no remaining `Flex::Rules` references in the codebase.

**Key considerations for review:**
- Verify no missed references to `Flex::Rules` exist (especially
string-based or dynamic references)
- Confirm this change is coordinated with any external consumers of
these classes
- Check that the Strata namespace integration follows existing patterns

Addresses Linear ticket **TSS-338**.

## Testing

- **All tests pass:** 798 examples, 0 failures, 1 pending
- **Lint checks pass:** 240 files inspected, no offenses detected  
- **Comprehensive search:** No remaining `Flex::Rules` references found
in codebase
- **Rails autoloading:** Classes are properly autoloaded in the new
Strata namespace

---

**Link to Devin run:**
https://app.devin.ai/sessions/3bfa5894ebdd45b5a1e501b4f56f6dfc
**Requested by:** @baonguyenNava

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: Bao Nguyen <baonguyen@navapbc.com>

Author: devin-ai-integration[bot]

app/models/flex/rules/medicaid_ruleset.rb app/models/strata/medicaid_ruleset.rbapp/models/flex/rules/medicaid_ruleset.rb renamed to app/models/strata/medicaid_ruleset.rb

@@ -1,8 +1,7 @@
-module Flex
-  module Rules
-    # Implements eligibility rules for Medicaid benefits.
-    # Handles age calculations, residency verification, and income-based qualification.
-    class MedicaidRuleset
+module Strata
+  # Implements eligibility rules for Medicaid benefits.
+  # Handles age calculations, residency verification, and income-based qualification.
+  class MedicaidRuleset
       def medicaid_eligibility(state_of_residence, age_over_65, modified_adjusted_gross_income)
         age_over_65 && modified_adjusted_gross_income < 50000
       end
@@ -30,6 +29,5 @@ def modified_adjusted_gross_income(annual_income, deductions)
         return 0 if annual_income < deductions
         annual_income - deductions
       end
-    end
   end
 end

…/models/flex/rules/paid_leave_ruleset.rb app/models/strata/paid_leave_ruleset.rbapp/models/flex/rules/paid_leave_ruleset.rb renamed to app/models/strata/paid_leave_ruleset.rb app/models/flex/rules/paid_leave_ruleset.rb renamed to app/models/strata/paid_leave_ruleset.rb

@@ -1,8 +1,7 @@
-module Flex
-  module Rules
-    # Implements eligibility rules for paid leave benefits based on Massachusetts PFML guidelines.
-    # Includes checks for submission timing, earnings requirements, and benefit calculations.
-    class PaidLeaveRuleset
+module Strata
+  # Implements eligibility rules for paid leave benefits based on Massachusetts PFML guidelines.
+  # Includes checks for submission timing, earnings requirements, and benefit calculations.
+  class PaidLeaveRuleset
       def submitted_within_60_days_of_leave_start(submitted_at, leave_starts_on)
         return nil if submitted_at.nil? || leave_starts_on.nil?
 
@@ -45,6 +44,5 @@ def base_period
 
       def individual_average_weekly_wage
       end
-    end
   end
 end

…dels/flex/rules/medicaid_ruleset_spec.rb …c/models/strata/medicaid_ruleset_spec.rbspec/models/flex/rules/medicaid_ruleset_spec.rb renamed to spec/models/strata/medicaid_ruleset_spec.rb spec/models/flex/rules/medicaid_ruleset_spec.rb renamed to spec/models/strata/medicaid_ruleset_spec.rb

@@ -1,8 +1,7 @@
 require 'rails_helper'
 
-module Flex
-  module Rules
-    RSpec.describe MedicaidRuleset do
+module Strata
+  RSpec.describe MedicaidRuleset do
       evaluated_on = Date.new(2025, 5, 28) # Freeze time for testing
       let(:rules) { described_class.new }
 
@@ -81,6 +80,5 @@ module Rules
           end
         end
       end
-    end
   end
 end

…ls/flex/rules/paid_leave_ruleset_spec.rb …models/strata/paid_leave_ruleset_spec.rbspec/models/flex/rules/paid_leave_ruleset_spec.rb renamed to spec/models/strata/paid_leave_ruleset_spec.rb spec/models/flex/rules/paid_leave_ruleset_spec.rb renamed to spec/models/strata/paid_leave_ruleset_spec.rb

@@ -1,8 +1,7 @@
 require 'rails_helper'
 
-module Flex
-  module Rules
-    RSpec.describe PaidLeaveRuleset do
+module Strata
+  RSpec.describe PaidLeaveRuleset do
       base_date = Date.new(2025, 7, 1)
       let(:rules) { described_class.new }
 
@@ -22,6 +21,5 @@ module Rules
           end
         end
       end
-    end
   end
 end