Task/DB-Migration: Add Key-Value to SQL Migration functionality. (#3380)

* feat(go): add db package;

* feat(go): add jobs table;

* feat(go): add schema migration facade;

* refactor(go): use custom key type to avoid collisions;

db/postgres.go

@@ -0,0 +1,49 @@
+package db
+
+import (
+	"fmt"
+	"github.com/gravitl/netmaker/servercfg"
+	"gorm.io/driver/postgres"
+	"gorm.io/gorm"
+	"gorm.io/gorm/logger"
+)
+
+// postgresConnector for initializing and
+// connecting to a postgres database.
+type postgresConnector struct{}
+
+// postgresConnector.connect connects and
+// initializes a connection to postgres.
+func (pg *postgresConnector) connect() (*gorm.DB, error) {
+	pgConf := servercfg.GetSQLConf()
+	dsn := fmt.Sprintf(
+		"host=%s port=%d user=%s password=%s dbname=%s sslmode=%s connect_timeout=5",
+		pgConf.Host,
+		pgConf.Port,
+		pgConf.Username,
+		pgConf.Password,
+		pgConf.DB,
+		pgConf.SSLMode,
+	)
+
+	db, err := gorm.Open(postgres.Open(dsn), &gorm.Config{
+		Logger: logger.Default.LogMode(logger.Silent),
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	// ensure netmaker_v1 schema exists.
+	err = db.Exec("CREATE SCHEMA IF NOT EXISTS netmaker_v1").Error
+	if err != nil {
+		return nil, err
+	}
+
+	// set the netmaker_v1 schema as the default schema.
+	err = db.Exec("SET search_path TO netmaker_v1").Error
+	if err != nil {
+		return nil, err
+	}
+
+	return db, nil
+}