Add instructions for postgresql timeseries migrations

backend/README.md

@@ -202,6 +202,35 @@ This is done automatically as part of the promotion workflows
 ([promoteToProduction](https://github.com/equinor/flotilla/blob/main/.github/workflows/promoteToProduction.yml)
 and [promoteToStaging](https://github.com/equinor/flotilla/blob/main/.github/workflows/promoteToStaging.yml)).
 
+## Database setup
+
+If reseting database, but still using postgresql (removing old migrations and adding them manually again), you need to manually add some migrations commands for the timeseries db.
+
+Add the following to the **top of the first migration's** `Up()` method:
+
+```
+            // MANUALLY ADDED:
+            // Adding timescale extension to the database
+            migrationBuilder.Sql("CREATE EXTENSION IF NOT EXISTS timescaledb CASCADE;");
+            //
+```
+
+**For each of the timeseries tables**, add the following to the **bottom of the last migration's** `Up()` method:
+
+```
+            migrationBuilder.Sql(
+                "SELECT create_hypertable( '\"TIME-TABLE-NAME\"', 'Time');\n"
+            );
+```
+
+Example:
+
+```
+            migrationBuilder.Sql(
+                "SELECT create_hypertable( '\"RobotBatteryTimeseries\"', 'Time');\n"
+            );
+```
+
 ## Formatting
 
 ### CSharpier