[AZ-189] [AZ-190] [AZ-191] [AZ-192] [AZ-193] [AZ-194] [AZ-195] Add e2e blackbox test suite

Made-with: Cursor

_docs/02_document/modules/common_database_schema_holder.md

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+# Module: Azaion.Common.Database.AzaionDbSchemaHolder
+
+## Purpose
+Static holder for the linq2db `MappingSchema` that maps C# entities to PostgreSQL table/column naming conventions and handles custom type conversions.
+
+## Public Interface
+
+| Member | Type | Description |
+|--------|------|-------------|
+| `MappingSchema` | `static readonly MappingSchema` | Pre-built schema with column name and type mappings |
+
+## Internal Logic
+Static constructor:
+1. Creates a `MappingSchema` with a global callback that converts all column names to snake_case via `StringExtensions.ToSnakeCase`.
+2. Uses `FluentMappingBuilder` to configure the `User` entity:
+   - Table name: `"users"`
+   - `Id`: primary key, `DataType.Guid`
+   - `Role`: stored as text, with custom conversion to/from `RoleEnum` via `Enum.Parse`
+   - `UserConfig`: stored as nullable JSON text, serialized/deserialized via `Newtonsoft.Json`
+
+## Dependencies
+- `User`, `RoleEnum` entities
+- `StringExtensions.ToSnakeCase`
+- linq2db `MappingSchema`, `FluentMappingBuilder`
+- `Newtonsoft.Json`
+
+## Consumers
+- `DbFactory.LoadOptions` — passes `MappingSchema` to `DataOptions.UseMappingSchema()`
+
+## Data Models
+Defines the ORM mapping for the `users` table.
+
+## Configuration
+None — all mappings are compile-time.
+
+## External Integrations
+None directly; mappings are used when queries execute against PostgreSQL.
+
+## Security
+None.
+
+## Tests
+None.