Insert broken when there's not primary key

[mathemancer]

Description

When a table does not have a primary key, attempting to use the UI to create a new record results in the backend throwing an unhandled 500 error.

Expected behavior

When a POST request representing a new empty record is sent for a table with no primary key, the server should respond with a 405 error, since we can't allow creating (or editing) rows on tables with no primary key. The error should be associated with some informational APIException stating that you can't insert into tables without a primary key.

The implementer should add an API test to validate their solution.

To Reproduce

1. Using psql or some other client, create a table without a primary key.
2. In the UI, navigate to that table.
3. Click the + to add a record.
   
4. Observe the 500 response.
5. See the error (via mouse-over) in the UI:
   
6. See the tuple index out of range error in the devtools.

[piyushupadhyay19]

Hi Everyone, I'm taking up this issue and have started working on it. I'll keep you updated on my progress.

[piyushupadhyay19]

Hey, I observed that the Mathesar web interface displays 'mathesar_tables' as a database. However, I couldn't connect to mathesar_tables database. I successfully connected to 'mathesar_django' database and made a table there using psql but I cannot find that table in UI because I think table needs to be created in mathesar_tables database and not mathesar_django database? Can you please clarify if 'mathesar_tables' is an alias for another database specified in my project's configuration, or if there's a different method to access it?

However, I successfully reproduced the issue, by making table through UI and then deleting the id column from it.