Refactor database interface to use *sql.DB directly

Simplified the database layer by removing custom interface wrappers
and using standard library *sql.DB and *sql.Tx types directly.

Changes:
- Removed DBConnection and DBTransaction interfaces from database.go
- Removed NewDBConnection() wrapper function
- Updated TokenGenerator to use *sql.DB instead of DBConnection
- Updated all validation and revocation methods to accept *sql.Tx
- Updated TableManager to work with *sql.DB directly
- Updated all tests to use db.Begin() instead of custom wrappers
- Fixed GeneratorConfig.DB field (was DBConn)
- Updated documentation in doc.go with correct API usage

Benefits:
- Simpler API with fewer abstractions
- Works directly with database/sql standard library
- Compatible with GORM (via gormDB.DB()) and Bun (share same *sql.DB)
- Easier to understand and maintain
- No unnecessary wrapper layers

Breaking changes:
- GeneratorConfig.DBConn renamed to GeneratorConfig.DB
- Removed NewDBConnection() function - pass *sql.DB directly
- ValidateAccess/ValidateRefresh now accept *sql.Tx instead of DBTransaction
- Token.Revoke/CheckNotRevoked now accept *sql.Tx instead of DBTransaction

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

hwsauth/model.go

@@ -2,7 +2,6 @@ package hwsauth
 
 import (
 	"context"
-	"database/sql"
 )
 
 type authenticatedModel[T Model] struct {
@@ -21,26 +20,39 @@ type Model interface {
 
 type ContextLoader[T Model] func(ctx context.Context) T
 
-type LoadFunc[T Model] func(tx *sql.Tx, id int) (T, error)
+type LoadFunc[T Model] func(tx DBTransaction, id int) (T, error)
 
 // Return a new context with the user added in
-func setAuthenticatedModel[T Model](ctx context.Context, m *authenticatedModel[T]) context.Context {
+func setAuthenticatedModel[T Model](ctx context.Context, m authenticatedModel[T]) context.Context {
 	return context.WithValue(ctx, "hwsauth context key authenticated-model", m)
 }
 
 // Retrieve a user from the given context. Returns nil if not set
-func getAuthorizedModel[T Model](ctx context.Context) *authenticatedModel[T] {
-	model, ok := ctx.Value("hwsauth context key authenticated-model").(*authenticatedModel[T])
-	if !ok {
-		return nil
+func getAuthorizedModel[T Model](ctx context.Context) (model authenticatedModel[T], ok bool) {
+	defer func() {
+		if r := recover(); r != nil {
+			// panic happened, return ok = false
+			ok = false
+			model = authenticatedModel[T]{}
+		}
+	}()
+	model, cok := ctx.Value("hwsauth context key authenticated-model").(authenticatedModel[T])
+	if !cok {
+		return authenticatedModel[T]{}, false
 	}
-	return model
+	return model, true
 }
 
 func (auth *Authenticator[T]) CurrentModel(ctx context.Context) T {
-	model := getAuthorizedModel[T](ctx)
-	if model == nil {
+	auth.logger.Debug().Any("context", ctx).Msg("")
+	if ctx == nil {
 		return getNil[T]()
 	}
+	model, ok := getAuthorizedModel[T](ctx)
+	if !ok {
+		result := getNil[T]()
+		auth.logger.Debug().Any("model", result).Msg("")
+		return result
+	}
 	return model.model
 }