Better compile error for entity without primary key

[billy1624]

PR Info

• Related issue Handle tables with no primary keys #485

Adds

• Better compile error for entity without primary key.

Before:

---- src/lib.rs - derive_entity_model (line 116) stdout ----
error[E0412]: cannot find type `PrimaryKey` in this scope
 --> src/lib.rs:119:35
  |
5 | #[derive(Clone, Debug, PartialEq, DeriveEntityModel)]
  |                                   ^^^^^^^^^^^^^^^^^
  |
  = note: this error originates in the derive macro `sea_orm::prelude::DeriveEntity` (in Nightly builds, run with -Z macro-backtrace for more info)
help: you might have meant to use the associated type
  |
5 | #[derive(Clone, Debug, PartialEq, Self::PrimaryKey)]
  |                                   ~~~~~~~~~~~~~~~~
help: consider importing one of these items
  |
2 | use sea_orm::tests_cfg::cake::PrimaryKey;
  |
2 | use sea_orm::tests_cfg::cake_expanded::PrimaryKey;
  |
2 | use sea_orm::tests_cfg::cake_filling::PrimaryKey;
  |
2 | use sea_orm::tests_cfg::cake_filling_price::PrimaryKey;
  |
    and 6 other candidates

error: aborting due to previous error

For more information about this error, try `rustc --explain E0412`.
Couldn't compile the test.

After:

---- src/lib.rs - derive_entity_model (line 116) stdout ----
error: Entity must have a primary key column. See <https://github.com/SeaQL/sea-orm/issues/485> for details.
 --> src/lib.rs:119:35
  |
5 | #[derive(Clone, Debug, PartialEq, DeriveEntityModel)]
  |                                   ^^^^^^^^^^^^^^^^^
  |
  = note: this error originates in the derive macro `DeriveEntityModel` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0277]: the trait bound `_doctest_main_src_lib_rs_116_0::PrimaryKey: sea_orm::IdenStatic` is not satisfied
  --> src/lib.rs:119:35
   |
5  | #[derive(Clone, Debug, PartialEq, DeriveEntityModel)]
   |                                   ^^^^^^^^^^^^^^^^^ the trait `sea_orm::IdenStatic` is not implemented for `_doctest_main_src_lib_rs_116_0::PrimaryKey`
   |
   = help: the following other types implement trait `sea_orm::IdenStatic`:
             CakeFillingPrice
             LunchSet
             RustKeyword
             SelectA
             SelectB
             _doctest_main_src_lib_rs_116_0::Column
             _doctest_main_src_lib_rs_116_0::Entity
             sea_orm::tests_cfg::Cake
           and 26 others
note: required by a bound in `sea_orm::PrimaryKeyTrait`
  --> /Applications/MAMP/htdocs/sea-orm/src/entity/primary_key.rs:40:28
   |
40 | pub trait PrimaryKeyTrait: IdenStatic + Iterable {
   |                            ^^^^^^^^^^ required by this bound in `sea_orm::PrimaryKeyTrait`
   = note: this error originates in the derive macro `DeriveEntityModel` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0277`.
Couldn't compile the test.

[tyt2y3]

Neat

[gitmalong]

In my case I am getting error messages for tables that have primary keys . See #2141