Query one non-optional

[sinder38]

Motivation

I frequently query one row of something using .one(db) method and return an error if its None.

It would be nice to have a distinction between fetching one row and fetching optional row since its quite common(like in sqlx).

Proposed Solutions

I propose to add another method to various query implementations, to query non-optional and return

sea-orm/src/error.rs

Lines 51 to 53 in 4f89d1b

	/// The record was not found in the database
	#[error("RecordNotFound Error: {0}")]
	RecordNotFound(String),

this error on None.

Additional Information

I think this feature would be relevant after error refactor proposed in one of the recent issues.
Naming this method seems a big problem as .one(db) is already taken for optional variant.
I can implement myself if needed.