Technically ambiguous reference docs for Field.primary_key

[Keryn Knight <django@…>]

In the ​Model Field Reference, the description for ​Field.primary_key says that Django will automatically add an IntegerField to hold the primary key - this is semi-correct, because Django actually provides an AutoField, itself internally represented as an IntegerField.

I've provided a proposed fix in ​this branch on GH. The only commit is ​this one, which boils down to two changes:

• Changed IntegerField to AutoField. This should be OK, as the AutoField documentation describes it being an IntegerField.
• Removed pluralisation in "for any fields in …", changing to "for any field in …" as there can be only one on a model.

[Tim Graham <timograham@…>]

In 218bbef0c4890b3b853dee945a02215533b923b7:

Fixed #19824 - Corrected the class described for Field.primary_key from IntegerField to AutoField.

Thanks Keryn Knight.

[Tim Graham <timograham@…>]

In ba794f68bfa86c2744e89adeb6027c9d6059d85e:

[1.5.x] Fixed #19824 - Corrected the class described for Field.primary_key from IntegerField to AutoField.

Thanks Keryn Knight.

Backport of 218bbef0c4 from master

[Tim Graham <timograham@…>]

In 57b62a74cb44ac3cf8b1a9d4cf75bfe953208814:

[1.4.x] Fixed #19824 - Corrected the class described for Field.primary_key from IntegerField to AutoField.

Thanks Keryn Knight.

Backport of 218bbef0c4 from master