Overridden get_lookup/get_transform not chainable

[Marc Tamlyn]

If a transform has an output_type which has a customised get_transform or get_lookup function, then it is not properly called.

[Marc Tamlyn]

Fixed in ​https://github.com/mjtamlyn/django/commit/253ef84bcf3c10660941301f81e92d02e43886c6

[Marc Tamlyn <marc.tamlyn@…>]

In a2dd618e3b4a7472fab852da450ca5eef92a922f:

Fixed #22648 -- Transform.output_type should respect overridden custom_lookup and custom_transform.

Previously, class lookups from the output_type would be used, but any
changes to custom_lookup or custom_transform would be ignored.

[Florian Apolloner]

Needs backport to 1.7, also see the fix in ​https://github.com/django/django/commit/5a2556afb9b1b3ef6e0622552970c67ac84ecd28 -- not sure if field_type should ever be None, please fix in the process of backporting.

[Marc Tamlyn <marc.tamlyn@…>]

In c38925a6018a7943936d1fd2b9038ab5de406545:

[1.7.x] Fixed #22648 -- Transform.output_type should respect overridden custom_lookup and custom_transform.

Previously, class lookups from the output_type would be used, but any
changes to custom_lookup or custom_transform would be ignored.

Backport of a2dd618 from master

[Marc Tamlyn <marc.tamlyn@…>]

In c38925a6018a7943936d1fd2b9038ab5de406545:

[1.7.x] Fixed #22648 -- Transform.output_type should respect overridden custom_lookup and custom_transform.

Previously, class lookups from the output_type would be used, but any
changes to custom_lookup or custom_transform would be ignored.

Backport of a2dd618 from master