Fix REG_DWORD handling in ConfigService.GetRegistryValue

[rodchristiansen]

Closes #4.

Summary

`GetRegistryValue` was reading raw values with `key?.GetValue(name) as string`, which returns null for any non-string registry type. `REG_DWORD` values come back from `RegistryKey.GetValue` as boxed `int`, so every CSP-deployed boolean or integer policy that used the standard DWORD wire format was silently dropped.

Affected helpers (all documented as `String/DWORD` in the README, but only actually working for string-typed deployments):

• `GetUseMtls`
• `GetAutoRotate`
• `GetSkipCertCheck`
• `GetCleanupOldProtectors`
• `GetKeyEscrowIntervalHours`
• `GetValidateKey`

The "Handle registry DWORD values" fall-through at `ConfigService.cs:115` in `GetRegistryBool` was unreachable.

Fix

Factor out `ConvertToConfigString` as an internal pure helper and route both production paths (`SOFTWARE\Policies...` and `SOFTWARE\Microsoft\PolicyManager...`) through it:

Raw type	Conversion
`string` (REG_SZ, REG_EXPAND_SZ)	Returned as-is; empty/whitespace → null
`int` (REG_DWORD)	Invariant-culture `int.ToString`
`long` (REG_QWORD)	Invariant-culture `long.ToString`
Anything else (REG_BINARY, REG_MULTI_SZ, …)	null → caller falls through

`GetRegistryBool` and `GetRegistryInt` now receive the string form of DWORDs and their existing `int.TryParse` branches light up correctly.

Tests (+22, 61 total, ~1s runtime)

New `RegistryValueConversionTests` class (joins `GlobalStateCollection` since it mutates `ConfigService` static state):

• 8 pure unit tests on `ConvertToConfigString` — null, empty/whitespace strings, positive/negative/zero/MaxValue/MinValue DWORDs, QWORD max, byte arrays and string arrays.
• 3 integration tests that open a real HKCU subkey via `TempRegistryKey.OpenKey()`, call `GetValue` on `REG_SZ` / `REG_DWORD` / `REG_QWORD` entries, and assert `ConvertToConfigString` returns the expected string. These prove the boxed-int/long round trip works against actual registry data — the part of the production chain that the old `as string` cast dropped.
• 4 end-to-end tests (`GetSkipCertCheck`, `GetKeyEscrowIntervalHours`, `GetAutoRotate`) exercising the full `GetRegistryBool`/`Int` path with DWORD values.

Test seam changes

• `TempRegistryKey.ReadValue` now delegates to `ConfigService.ConvertToConfigString` instead of having its own private switch, so production and test conversion logic can never drift apart.
• New `TempRegistryKey.OpenKey()` returns the underlying HKCU key so tests can exercise the raw `GetValue` chain directly.
• New `TempRegistryKey.SetQword()` for QWORD coverage.

Test plan

• `dotnet build CryptEscrow.sln` — 0 warnings, 0 errors
• `dotnet test CryptEscrow.sln -c Release` — 61 passed, 0 failed in ~1s
• CI run on this PR passes
• Manual verification: deploy `UseMtls` as `REG_DWORD = 1` via Intune CSP on a test box and confirm `GetUseMtls()` returns `true` after this change

[Copilot]

Pull request overview

Fixes ConfigService.GetRegistryValue so enterprise policy registry values stored as REG_DWORD/REG_QWORD are no longer silently ignored, enabling CSP-deployed boolean/integer policies to work as documented.

Changes:

• Refactors GetRegistryValue to read raw registry values and convert supported types via a new ConvertToConfigString helper.
• Updates the TempRegistryKey test fixture to reuse production conversion logic and adds helpers to support QWORD + raw RegistryKey.GetValue() testing.
• Adds RegistryValueConversionTests with unit + integration + end-to-end coverage for DWORD/QWORD conversions and affected getters.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/CryptEscrow/Services/ConfigService.cs	Adds ConvertToConfigString and routes both registry paths through shared raw-value conversion logic.
tests/CryptEscrow.Tests/Fixtures/TempRegistryKey.cs	Aligns fixture registry reads with production conversion and adds QWORD + direct key access for integration tests.
tests/CryptEscrow.Tests/Services/RegistryValueConversionTests.cs	Adds regression coverage for conversion and end-to-end DWORD policy parsing.

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