alembic: make user_gateway_credentials migration idempotent

Check if table/indexes already exist before creating.
Prevents DuplicateTable error when upgrading from RC2 which
created the same schema under different revision IDs.

Author: Olivier Gintrand

mcpgateway/alembic/versions/a1b2c3d4e5f6_add_user_gateway_credentials_table.py

@@ -10,6 +10,7 @@
 # Third-Party
 from alembic import op
 import sqlalchemy as sa
+from sqlalchemy import inspect
 
 # revision identifiers, used by Alembic.
 revision = "a1b2c3d4e5f6"
@@ -19,20 +20,29 @@
 
 
 def upgrade() -> None:
-    op.create_table(
-        "user_gateway_credentials",
-        sa.Column("id", sa.String(36), primary_key=True),
-        sa.Column("gateway_id", sa.String(36), sa.ForeignKey("gateways.id", ondelete="CASCADE"), nullable=False),
-        sa.Column("app_user_email", sa.String(255), sa.ForeignKey("email_users.email", ondelete="CASCADE"), nullable=False),
-        sa.Column("credential_type", sa.String(50), nullable=False),
-        sa.Column("credential_value", sa.Text(), nullable=False),
-        sa.Column("label", sa.String(255), nullable=True),
-        sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now()),
-        sa.Column("updated_at", sa.DateTime(timezone=True), server_default=sa.func.now(), onupdate=sa.func.now()),
-        sa.UniqueConstraint("gateway_id", "app_user_email", name="uq_credential_gateway_user"),
-    )
-    op.create_index("idx_user_credentials_gateway", "user_gateway_credentials", ["gateway_id"])
-    op.create_index("idx_user_credentials_email", "user_gateway_credentials", ["app_user_email"])
+    conn = op.get_bind()
+    inspector = inspect(conn)
+    existing_tables = inspector.get_table_names()
+
+    if "user_gateway_credentials" not in existing_tables:
+        op.create_table(
+            "user_gateway_credentials",
+            sa.Column("id", sa.String(36), primary_key=True),
+            sa.Column("gateway_id", sa.String(36), sa.ForeignKey("gateways.id", ondelete="CASCADE"), nullable=False),
+            sa.Column("app_user_email", sa.String(255), sa.ForeignKey("email_users.email", ondelete="CASCADE"), nullable=False),
+            sa.Column("credential_type", sa.String(50), nullable=False),
+            sa.Column("credential_value", sa.Text(), nullable=False),
+            sa.Column("label", sa.String(255), nullable=True),
+            sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now()),
+            sa.Column("updated_at", sa.DateTime(timezone=True), server_default=sa.func.now(), onupdate=sa.func.now()),
+            sa.UniqueConstraint("gateway_id", "app_user_email", name="uq_credential_gateway_user"),
+        )
+
+    existing_indexes = {idx["name"] for idx in inspector.get_indexes("user_gateway_credentials")}
+    if "idx_user_credentials_gateway" not in existing_indexes:
+        op.create_index("idx_user_credentials_gateway", "user_gateway_credentials", ["gateway_id"])
+    if "idx_user_credentials_email" not in existing_indexes:
+        op.create_index("idx_user_credentials_email", "user_gateway_credentials", ["app_user_email"])
 
 
 def downgrade() -> None: