az postgres flexible-server db create causes InternalServerError

While creating posgres (flexible server) database:
`az postgres flexible-server db create --server-name some-postgresql-server-1 --resource-group myTFResourceGroup --database-name exampledb --charset utf8 --collation ucs_basic`
I get the following error message:
```
(InternalServerError) An unexpected error occured while processing the request. Tracking ID: '6edb273a-5244-4b56-967a-b6ff63243725'
Code: InternalServerError
Message: An unexpected error occured while processing the request. Tracking ID: '6edb273a-5244-4b56-967a-b6ff63243725'
```
After spending few hours I discovered that the problem was no with the server stability itself but with the collation set to ucs_basic. After removing charset and collation it worked with default values:

> Creating database with utf8 charset and en_US.utf8 collation

It worked as well for:
--charset utf8 --collation pl_PL.utf8
--charset utf8 --collation en_US
--charset utf8 --collation pl_PL
But not for:
--charset utf8 --collation pl

Life would be easier with more verbose messages.