refactor: add _id to all model interfaces

[mantariksh]

Problem

We have two interfaces for each model, one for plain objects and one for Mongoose documents. For example, we have IForm for plain Form objects, and IFormSchema for documents retrieved from the database. However, none of our interfaces for plain objects include an _id key, despite the fact that all objects retrieved from the database have an _id key which we frequently access. This makes it difficult for us to write typed code for objects retrieved from the database, as every time we need to access the _id key, we have to create a union type.

Solution

Add an _id key to all relevant interfaces. The following interfaces were excluded because we set _id: false in the schema:

• Form logo
• Custom form logo
• MyInfo schema (part of baseField)
• Columns in table fields

The disadvantage of this approach is that when declaring new documents to add to the database, we have to omit _id from the type, as can be seen in sms_count.server.model.ts. However, I think this is a tiny minority of cases compared to the number of cases where we need the _id key to be present.

[karrui]

lgtm

[mantariksh]

No idea why build keeps failing, will investigate tmr

[karrui]

I removed _id from form again, since we stopped using IForm directly and use IFormSchema nowadays, which has the _id field