Add reference to BLSample, describe position type (#266)

Author: gfrn

schemas/ispyb/updates/2025_04_11_Position_blSampleId_positionType.sql

@@ -0,0 +1,10 @@
+INSERT IGNORE INTO SchemaStatus (scriptName, schemaStatus) VALUES ('2025_04_11_Position_blSampleId_positionType.sql', 'ONGOING');
+
+ALTER TABLE Position
+  ADD positionType varchar(45) COMMENT 'Action (type) that originated this position',
+  ADD blSampleId int(11) unsigned COMMENT 'FK, references parent sample',
+  ADD CONSTRAINT `Position_fk_blSampleId`
+    FOREIGN KEY (`blSampleId`)
+      REFERENCES `BLSample` (`blSampleId`);
+
+UPDATE SchemaStatus SET schemaStatus = 'DONE' WHERE scriptName = '2025_04_11_Position_blSampleId_positionType.sql';