feat: 扩展多个字符串列为 TEXT 类型并添加 tls-client 可选依赖

数据库迁移:
- 扩展 provider_api_keys.api_key 为 TEXT（OAuth tokens 可能很长）
- 扩展 ldap_configs 的 bind_dn、base_dn、user_search_filter 为 TEXT
- 扩展 oauth_providers.client_id 为 TEXT
- 添加 SQLite 兼容支持（batch 模式）
- 添加表/列存在性检查

依赖:
- 添加 tls-client 作为可选依赖 [tls]

alembic/versions/20260204_1500_b5c6d7e8f9a0_expand_api_key_column_to_text.py

@@ -1,7 +1,7 @@
-"""Add provider_type and expand api_key column to TEXT
+"""Add provider_type and expand string columns to TEXT
 
 - Add providers.provider_type (String(20), server_default="custom")
-- Change provider_api_keys.api_key from VARCHAR(500) to TEXT (OAuth tokens can be long)
+- Expand multiple VARCHAR columns to TEXT for long values (OAuth tokens, LDAP DN, URLs, etc.)
 
 Revision ID: b5c6d7e8f9a0
 Revises: c4e8f9a1b2c3
@@ -22,6 +22,16 @@ branch_labels: Union[str, Sequence[str], None] = None
 depends_on: Union[str, Sequence[str], None] = None
 
 
+# 需要扩展为 TEXT 的列（表名, 列名, 原始类型长度）
+COLUMNS_TO_EXPAND = [
+    ("provider_api_keys", "api_key", 500),  # OAuth tokens can be very long
+    ("ldap_configs", "bind_dn", 255),  # LDAP DN can be deeply nested
+    ("ldap_configs", "base_dn", 255),  # LDAP DN can be deeply nested
+    ("ldap_configs", "user_search_filter", 500),  # Complex LDAP filters
+    ("oauth_providers", "client_id", 255),  # Some OAuth providers use JWT client_id
+]
+
+
 def column_exists(table_name: str, column_name: str) -> bool:
     """检查列是否已存在"""
     bind = op.get_bind()
@@ -30,6 +40,72 @@ def column_exists(table_name: str, column_name: str) -> bool:
     return column_name in columns
 
 
+def table_exists(table_name: str) -> bool:
+    """检查表是否存在"""
+    bind = op.get_bind()
+    inspector = inspect(bind)
+    return table_name in inspector.get_table_names()
+
+
+def is_sqlite() -> bool:
+    """检查是否为 SQLite 数据库"""
+    bind = op.get_bind()
+    return bind.dialect.name == "sqlite"
+
+
+def expand_column_to_text(table_name: str, column_name: str, original_length: int) -> None:
+    """将 VARCHAR 列扩展为 TEXT（兼容 SQLite）"""
+    if not table_exists(table_name):
+        return
+    if not column_exists(table_name, column_name):
+        return
+
+    if is_sqlite():
+        # SQLite 不支持直接 ALTER COLUMN，需要用 batch 模式
+        with op.batch_alter_table(table_name) as batch_op:
+            batch_op.alter_column(
+                column_name,
+                type_=sa.Text(),
+                existing_type=sa.String(original_length),
+            )
+    else:
+        op.alter_column(
+            table_name,
+            column_name,
+            type_=sa.Text(),
+            existing_type=sa.String(original_length),
+        )
+
+
+def shrink_column_to_varchar(
+    table_name: str, column_name: str, target_length: int, nullable: bool = False
+) -> None:
+    """将 TEXT 列缩小为 VARCHAR（兼容 SQLite）
+    WARNING: 如果数据超过 target_length 会失败
+    """
+    if not table_exists(table_name):
+        return
+    if not column_exists(table_name, column_name):
+        return
+
+    if is_sqlite():
+        with op.batch_alter_table(table_name) as batch_op:
+            batch_op.alter_column(
+                column_name,
+                type_=sa.String(target_length),
+                existing_type=sa.Text(),
+                existing_nullable=nullable,
+            )
+    else:
+        op.alter_column(
+            table_name,
+            column_name,
+            type_=sa.String(target_length),
+            existing_type=sa.Text(),
+            existing_nullable=nullable,
+        )
+
+
 def upgrade() -> None:
     # Add providers.provider_type
     if not column_exists("providers", "provider_type"):
@@ -38,26 +114,16 @@ def upgrade() -> None:
             sa.Column("provider_type", sa.String(20), nullable=False, server_default="custom"),
         )
 
-    # Expand provider_api_keys.api_key from VARCHAR(500) to TEXT
-    op.alter_column(
-        "provider_api_keys",
-        "api_key",
-        type_=sa.Text(),
-        existing_type=sa.String(500),
-        existing_nullable=False,
-    )
+    # Expand VARCHAR columns to TEXT
+    for table_name, column_name, original_length in COLUMNS_TO_EXPAND:
+        expand_column_to_text(table_name, column_name, original_length)
 
 
 def downgrade() -> None:
-    # Revert provider_api_keys.api_key from TEXT to VARCHAR(500)
-    # WARNING: Downgrade may fail if any api_key values exceed 500 characters
-    op.alter_column(
-        "provider_api_keys",
-        "api_key",
-        type_=sa.String(500),
-        existing_type=sa.Text(),
-        existing_nullable=False,
-    )
+    # Shrink TEXT columns back to VARCHAR
+    # WARNING: Downgrade may fail if any values exceed original length
+    for table_name, column_name, original_length in reversed(COLUMNS_TO_EXPAND):
+        shrink_column_to_varchar(table_name, column_name, original_length)
 
     # Drop providers.provider_type
     if column_exists("providers", "provider_type"):