chore: add migration guide doc

Author: blockchainluffy

rolling-shutter/migration-guide-dev.md

@@ -0,0 +1,60 @@
+# Database Migration Guide for Keyper Implementations
+
+This guide explains how to create and manage database migrations for any keyper
+implementation in the Rolling Shutter project.
+
+## Overview
+
+Database migrations are automatically executed when running the `initdb` command
+for all keyper implementations. This ensures that each keyper's database schema
+is properly initialized and updated to the latest version.
+
+## Migration Requirements
+
+All migrations must adhere to the following prerequisites:
+
+### 1. File Location
+
+Migrations must be stored in the following directory structure:
+
+```
+keyperimpl/{keyper_name}/database/sql/migrations/
+```
+
+Where `{keyper_name}` represents the specific keyper implementation (e.g.,
+`gnosis`, `optimism`, `shutterservice`, etc.).
+
+### 2. File Format and Naming Convention
+
+- **File Format**: All migrations must be written in SQL
+- **Naming Convention**: Files must follow a strict versioning pattern:
+  ```
+  V{version_number}_{migration_description}.sql
+  ```
+
+#### Examples:
+
+- `V2_validatorRegistrations.sql`
+- `V3_addUserTable.sql`
+- `V4_updateIndexes.sql`
+
+#### Version Number Rules:
+
+- **Minimum Version**: The lowest allowed version number is **2**
+- **Version 1**: Represents the initial database schema (automatically created)
+- **Sequential Ordering**: All subsequent migrations must have version numbers
+  greater than any previously defined migration
+
+### 3. Version Tracking
+
+- Migration version records are maintained in the `meta_inf` table for each
+  keyper
+- This tracking system ensures that only new migrations are executed when the
+  `initdb` command is run again
+- The system automatically detects which migrations have already been applied
+
+## Important Limitations
+
+**No Rollback Support**: The migration system does not support rolling back to
+previous versions. Once a migration is applied, it cannot be undone through the
+automated migration system.