feat: add database block count to prometheus to improve alert monitor…

…ing (#74)

Fixes [BDU-542](https://forbole.atlassian.net/browse/BDU-542)

- [x] Targeted PR against correct branch.
- [x] Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
- [ ] Wrote unit tests.
- [x] Re-reviewed `Files changed` in the Github PR explorer.

database/postgresql/postgresql.go

@@ -123,6 +123,17 @@ VALUES ($1, $2, $3, $4, $5, $6) ON CONFLICT DO NOTHING`
 	return err
 }
 
+// GetTotalBlocks implements database.Database
+func (db *Database) GetTotalBlocks() int64 {
+	var blockCount int64
+	err := db.Sql.QueryRow(`SELECT count(*) FROM block;`).Scan(&blockCount)
+	if err != nil {
+		return 0
+	}
+
+	return blockCount
+}
+
 // SaveTx implements database.Database
 func (db *Database) SaveTx(tx *types.Tx) error {
 	var partitionID int64