Validate schema again, including number of columns.

Author: rkistner

packages/powersync/lib/src/database/native/native_powersync_database.dart

@@ -261,6 +261,7 @@ class PowerSyncDatabaseImpl
     if (disconnecter != null) {
       throw AssertionError('Cannot update schema while connected');
     }
+    schema.validate();
     this.schema = schema;
     return updateSchemaInIsolate(database, schema);
   }

packages/powersync/lib/src/schema.dart

@@ -11,6 +11,12 @@ class Schema {
   const Schema(this.tables);
 
   Map<String, dynamic> toJson() => {'tables': tables};
+
+  void validate() {
+    for (var table in tables) {
+      table.validate();
+    }
+  }
 }
 
 /// A single table in the schema.
@@ -106,6 +112,12 @@ class Table {
 
       columnNames.add(column.name);
     }
+
+    if (columns.length > 63) {
+      throw AssertionError(
+          "Table $name has ${columns.length} columns, maximum is 63.");
+    }
+
     Set<String> indexNames = {};
 
     for (var index in indexes) {