adds a flag for specifying the db name for migrations (#185)

## Problem
Currently, it seems that the name of the target database for migrations
is fixed to "default." This produces the following error when there is
no database named "default":
```
problem applying Hasura metadata: problem adding metadata for the buckets table: status_code: 400\nresponse: {"error":"source with name \"default\" does not exist","path":"$.args","code":"not-exists"}
```
(see
#184 (comment))

## Solution
To address this issue and provide more flexibility in configuring the
target database for migrations, we propose the following solution:

- **Environment Variable**: Introduce a new environment variable named
`HASURA_DB_NAME` to allow users to specify the target database name for
migrations.

- **Configuration Update**: Modify the code in
`hasura-storage/migrations/hasura.go` to use the value of
`HASURA_DB_NAME` as the target database name. This ensures that users
can configure the target database dynamically.

- **Fallback to "default"**: If `HASURA_DB_NAME` is not set, the code
should default to "default" to maintain backward compatibility.

## Notes
- Users can set the `HASURA_DB_NAME` environment variable to configure
the target database for migrations to their desired database name.

- This change enhances the flexibility of the migration process,
especially in cases where the database name is not "default."

- Reviewers are encouraged to verify that the documentation has been
updated to reflect the new configuration option.

With this solution, users can customize the target database for
migrations by setting the `HASURA_DB_NAME` environment variable, which
eliminates the error associated with the fixed "default" database name.

cmd/serve.go

@@ -42,6 +42,7 @@ const (
 	corsAllowOriginsFlag         = "cors-allow-origins"
 	corsAllowCredentialsFlag     = "cors-allow-credentials" //nolint: gosec
 	clamavServerFlag             = "clamav-server"
+	hasuraDbNameFlag             = "hasura-db-name"
 )
 
 func ginLogger(logger *logrus.Logger) gin.HandlerFunc {
@@ -158,6 +159,7 @@ func applymigrations(
 	hasuraMetadata bool,
 	hasuraEndpoint string,
 	hasuraSecret string,
+	hasuraDbName string,
 	logger *logrus.Logger,
 ) {
 	if postgresMigrations {
@@ -174,7 +176,7 @@ func applymigrations(
 
 	if hasuraMetadata {
 		logger.Info("applying hasura metadata")
-		if err := migrations.ApplyHasuraMetadata(hasuraEndpoint, hasuraSecret); err != nil {
+		if err := migrations.ApplyHasuraMetadata(hasuraEndpoint, hasuraSecret, hasuraDbName); err != nil {
 			logger.Errorf("problem applying hasura metadata: %s", err.Error())
 			os.Exit(1)
 		}
@@ -222,6 +224,7 @@ func init() {
 			"",
 			"postgres connection, i.e. postgres://user@pass:localhost:5432/mydb",
 		)
+		addStringFlag(serveCmd.Flags(), hasuraDbNameFlag, "default", "Hasura database name")
 	}
 
 	{
@@ -275,6 +278,7 @@ var serveCmd = &cobra.Command{
 				s3BucketFlag:           viper.GetString(s3BucketFlag),
 				s3RootFolderFlag:       viper.GetString(s3RootFolderFlag),
 				clamavServerFlag:       viper.GetString(clamavServerFlag),
+				hasuraDbNameFlag:       viper.GetString(hasuraDbNameFlag),
 			},
 		).Debug("parameters")
 
@@ -294,6 +298,7 @@ var serveCmd = &cobra.Command{
 			viper.GetBool(hasuraMetadataFlag),
 			viper.GetString(hasuraEndpointFlag),
 			viper.GetString(hasuraAdminSecretFlag),
+			viper.GetString(hasuraDbNameFlag),
 			logger,
 		)
 

migrations/hasura.go

@@ -142,11 +142,11 @@ type DropRelationshipArgs struct {
 	Relationship string `json:"relationship"`
 }
 
-func ApplyHasuraMetadata(url, hasuraSecret string) error { //nolint: funlen
+func ApplyHasuraMetadata(url, hasuraSecret, hasuraDbName string) error { //nolint: funlen
 	bucketsTable := TrackTable{
 		Type: "pg_track_table",
 		Args: PgTrackTableArgs{
-			Source: "default",
+			Source: hasuraDbName,
 			Table: Table{
 				Schema: "storage",
 				Name:   "buckets",
@@ -185,7 +185,7 @@ func ApplyHasuraMetadata(url, hasuraSecret string) error { //nolint: funlen
 	filesTable := TrackTable{
 		Type: "pg_track_table",
 		Args: PgTrackTableArgs{
-			Source: "default",
+			Source: hasuraDbName,
 			Table: Table{
 				Schema: "storage",
 				Name:   "files",
@@ -227,7 +227,7 @@ func ApplyHasuraMetadata(url, hasuraSecret string) error { //nolint: funlen
 	virusTable := TrackTable{
 		Type: "pg_track_table",
 		Args: PgTrackTableArgs{
-			Source: "default",
+			Source: hasuraDbName,
 			Table: Table{
 				Schema: "storage",
 				Name:   "virus",
@@ -270,7 +270,7 @@ func ApplyHasuraMetadata(url, hasuraSecret string) error { //nolint: funlen
 				Name:   "files",
 			},
 			Name:   "bucket",
-			Source: "default",
+			Source: hasuraDbName,
 			Using: CreateObjectRelationshipUsing{
 				ForeignKeyConstraintOn: []string{"bucket_id"},
 			},
@@ -289,7 +289,7 @@ func ApplyHasuraMetadata(url, hasuraSecret string) error { //nolint: funlen
 				Name:   "buckets",
 			},
 			Name:   "files",
-			Source: "default",
+			Source: hasuraDbName,
 			Using: CreateArrayRelationshipUsing{
 				ForeignKeyConstraintOn: ForeignKeyConstraintOn{
 					Table: Table{
@@ -314,7 +314,7 @@ func ApplyHasuraMetadata(url, hasuraSecret string) error { //nolint: funlen
 				Name:   "virus",
 			},
 			Name:   "file",
-			Source: "default",
+			Source: hasuraDbName,
 			Using: CreateObjectRelationshipUsing{
 				ForeignKeyConstraintOn: []string{"file_id"},
 			},