MM-31356: Add a minimum required version check for Postgres (#16597)

* MM-31356: Add a minimum required version check for Postgres

To keep conformance with our failing fast and obvious philosophy,
we add a check to prevent Mattermost server from starting
if the postgres version is below 10.0.

This gives customers a chance to upgrade their database before upgrading
their Mattermost version, than to run into weird compatibility issues
after they have finished the upgrade.

https://mattermost.atlassian.net/browse/MM-31356

```release-note
NONE
```

* fix lint errors

* Use a function to pretty-print version string

* rectify comment

store/storetest/mocks/Store.go

@@ -236,20 +236,20 @@ func (_m *Store) GetCurrentSchemaVersion() string {
 	return r0
 }
 
-// GetDbVersion provides a mock function with given fields:
-func (_m *Store) GetDbVersion() (string, error) {
-	ret := _m.Called()
+// GetDbVersion provides a mock function with given fields: numerical
+func (_m *Store) GetDbVersion(numerical bool) (string, error) {
+	ret := _m.Called(numerical)
 
 	var r0 string
-	if rf, ok := ret.Get(0).(func() string); ok {
-		r0 = rf()
+	if rf, ok := ret.Get(0).(func(bool) string); ok {
+		r0 = rf(numerical)
 	} else {
 		r0 = ret.Get(0).(string)
 	}
 
 	var r1 error
-	if rf, ok := ret.Get(1).(func() error); ok {
-		r1 = rf()
+	if rf, ok := ret.Get(1).(func(bool) error); ok {
+		r1 = rf(numerical)
 	} else {
 		r1 = ret.Error(1)
 	}

store/storetest/store.go

@@ -95,7 +95,7 @@ func (s *Store) Close()                                { /* do nothing */ }
 func (s *Store) LockToMaster()                         { /* do nothing */ }
 func (s *Store) UnlockFromMaster()                     { /* do nothing */ }
 func (s *Store) DropAllTables()                        { /* do nothing */ }
-func (s *Store) GetDbVersion() (string, error)         { return "", nil }
+func (s *Store) GetDbVersion(bool) (string, error)     { return "", nil }
 func (s *Store) RecycleDBConnections(time.Duration)    {}
 func (s *Store) TotalMasterDbConnections() int         { return 1 }
 func (s *Store) TotalReadDbConnections() int           { return 1 }