Fix insertion of records to non-default schema table using raw SQL

[aidanharan]

Fix the insertion of records to non-default schema table that has identity column using raw SQL. This fixes https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/issues/1050

If you tried to insert records into a table that has an identity column (id in this case) using exec_insert:

connection.exec_insert("insert into [test].[aliens] (id, name) VALUES(1, 'Trisolarans'), (2, 'Xenomorph')"

Then the adapter would first need to turn on IDENTITY_INSERT for the table first. However, instead of running:

SET IDENTITY_INSERT [test].[aliens] ON;

The adapter was ignoring the table schema and trying to turn on IDENTITY_INSERT for the table in the default schema.

SET IDENTITY_INSERT [aliens] ON;

If a table of the same name did not exist in the default schema then an error would be thrown by SET IDENTITY_INSERT. If table of the same name in the default schema did exist then the INSERT query would fail as it would be unable to insert into the identity column.

Note: This is not a new issue. The issue was present in at least v7.0.2.0/7.0.1.0/6.1.3.0 of the gem.

[aidanharan]

@rgeerts Would you mind reviewing this PR? Thanks Aidan

[rgeerts]

I will look at it and give it a try to see if it works in my situation

[rgeerts]

Things ran fine for me and this looks good to me. Thanks!!