Inverting deps on SQL, Log and MQ plugins to make them optional dependencies of extended servers, Removing some dead code that brought in unused dependencies Filtering out some non-linux transitive deps. (#1057)

* initial Db helper split - make SQL and datastore packages optional

* abstracting log store

* break out DB, MQ and log drivers as extensions

* cleanup

* fewer deps

* fixing docker test

* hmm dbness

* updating db startup

* Consolidate all your extensions into one convenient package

* cleanup

* clean up dep constraints

api/datastore/sql/postgres/postgres.go

@@ -0,0 +1,63 @@
+package postgres
+
+import (
+	"github.com/fnproject/fn/api/datastore/sql/dbhelper"
+	_ "github.com/go-sql-driver/mysql"
+	"github.com/jmoiron/sqlx"
+	"github.com/lib/pq"
+	"net/url"
+)
+
+type postgresHelper int
+
+func (postgresHelper) Supports(scheme string) bool {
+	switch scheme {
+	case "postgres", "pgx":
+		return true
+	}
+	return false
+}
+
+func (postgresHelper) PreConnect(url *url.URL) (string, error) {
+	return url.String(), nil
+}
+
+func (postgresHelper) PostCreate(db *sqlx.DB) (*sqlx.DB, error) {
+	return db, nil
+
+}
+func (postgresHelper) CheckTableExists(tx *sqlx.Tx, table string) (bool, error) {
+	query := tx.Rebind(`SELECT count(*)
+	FROM information_schema.TABLES
+	WHERE TABLE_NAME = 'apps'
+`)
+
+	row := tx.QueryRow(query)
+
+	var count int
+	err := row.Scan(&count)
+	if err != nil {
+		return false, err
+	}
+
+	exists := count > 0
+	return exists, nil
+}
+
+func (postgresHelper) String() string {
+	return "postgres"
+}
+
+func (postgresHelper) IsDuplicateKeyError(err error) bool {
+	switch dbErr := err.(type) {
+	case *pq.Error:
+		if dbErr.Code == "23505" {
+			return true
+		}
+	}
+	return false
+}
+
+func init() {
+	dbhelper.Add(postgresHelper(0))
+}