Add support for composite keys

[qadirpervez]

The schema:build command generates a JSON file containing schema information. However, when a table has multiple columns combined as a primary key, the generated JSON only includes the first column as the primary key. This behavior is inconsistent with expectations, as it should provide information for all columns in the composite primary key.

Current Behavior

CREATE TABLE example_table (
    column1 INT,
    column2 INT,
    PRIMARY KEY (column1, column2)
);

schema:build generates:

"example_table ": {
	"name": "example_table",
	"type": "table",
	"columns": {
		"column1": {
			"name": "column1",
			"type": "INT",
			"primaryKey": true
		},
		"column2": {
			"name": "column2",
			"type": "INT",
			"primaryKey": false
		}
	},
	"primaryKey": "column1"
},

Expected Behavior

CREATE TABLE example_table (
    column1 INT,
    column2 INT,
    PRIMARY KEY (column1, column2)
);

schema:build to generate:

"example_table ": {
	"name": "example_table",
	"type": "table",
	"columns": {
		"column1": {
			"name": "column1",
			"type": "INT",
			"primaryKey": true
		},
		"column2": {
			"name": "column2",
			"type": "INT",
			"primaryKey": true
		}
	},
	"primaryKey": ["column1", "column2"]
},