Bring the other four providers' AssertValidIdentifier in line with PostgreSQL (weasel#416) - #420

Possible null reference return.

Possible null reference argument for parameter 'connectionString' in 'string IDatabaseProvider.AddApplicationNameToConnectionString(string connectionString, string applicationName)'.

Invalid type for parameter Weasel.Core.MultiTenancy.IGlobalLock{TConnection} in XML comment cref attribute: 'DatabaseBase{TConnection}.ApplyAllConfiguredChangesToDatabaseAsync(Weasel.Core.MultiTenancy.IGlobalLock{TConnection}, JasperFx.AutoCreate?, ReconnectionOptions?, System.Threading.CancellationToken)'

Type parameter 'TCommand' has no matching typeparam tag in the XML comment on 'CommandBuilderExtensions.FetchListAsync<T, TCommand>(DbConnection, ICommandBuilder<TCommand>, Func<DbDataReader, CancellationToken, Task<T>>, DbTransaction?, CancellationToken)' (but other type parameters do)

Dereference of a possibly null reference.

Dereference of a possibly null reference.

Possible null reference return.

Non-nullable property 'Id' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.

Possible null reference return.