PLT-7223: Update "Database schema cannot be upgraded" error message to indicate expected version (#7079)

* PLT-7223: Updated error message to include relevant schema versions

* PLT-7223: Removed unit test. It poisons database state, and there's no recovery mechanism, because the code under test causes an ungraceful exit, so we can't fix the database in a defer statement. This causes the next test execution or server start to fail.

* PLT-7223: Incorporated @crspeller's suggestions into error message string

i18n/en.json

@@ -5261,7 +5261,7 @@
   },
   {
     "id": "store.sql.schema_version.critical",
-    "translation": "The database schema version of %v cannot be upgraded.  You must not skip a version."
+    "translation": "Database schema version %v is no longer supported. This Mattermost server supports automatic upgrades from schema version %v through schema version %v. Downgrades are not supported. Please manually upgrade to at least version %v before continuing"
   },
   {
     "id": "store.sql.short_ciphertext",

store/sql_upgrade.go

@@ -28,6 +28,7 @@ const (
 	VERSION_3_2_0            = "3.2.0"
 	VERSION_3_1_0            = "3.1.0"
 	VERSION_3_0_0            = "3.0.0"
+	OLDEST_SUPPORTED_VERSION = VERSION_3_0_0
 )
 
 const (
@@ -66,7 +67,7 @@ func UpgradeDatabase(sqlStore SqlStore) {
 
 	// If we're not on the current version then it's too old to be upgraded
 	if sqlStore.GetCurrentSchemaVersion() != model.CurrentVersion {
-		l4g.Critical(utils.T("store.sql.schema_version.critical"), sqlStore.GetCurrentSchemaVersion())
+		l4g.Critical(utils.T("store.sql.schema_version.critical"), sqlStore.GetCurrentSchemaVersion(), OLDEST_SUPPORTED_VERSION, model.CurrentVersion, OLDEST_SUPPORTED_VERSION)
 		time.Sleep(time.Second)
 		os.Exit(EXIT_TOO_OLD)
 	}