add a way to display transitions of related models into admin

[DorianArdian]

Objectives

This change add a way to display transitions that are defined in related models (foreign keys, one to one fields) into models admins.

Example

In the example below, the car admin we will be able to display wheel transitions

class Wheel(BaseModel):
    orientation = FSMField(default="CENTER", choices=["LEFT", "CENTER", "RIGHT"], protected=True)

    @transition(
        field=orientation,
        source=["CENTER"],
        target="LEFT",
        custom=dict(admin=True),
    )
    def turn_left(self):
        pass

class Car(BaseModel):
    status = FSMField(default="STOP", choices=["STOP", "START"], protected=True)

    wheel = models.OneToOneField(
        Wheel,
        related_name="car",
        on_delete=models.CASCADE,
        null=True,
        blank=True,
    )

    @transition(
        field=status,
        source=["STOP"],
        target="START",
        custom=dict(admin=True),
    )
    def start(self):
        pass

@admin.register(Car)
class CarAdmin(FSMTransitionMixin, admin.ModelAdmin):
    readonly_fields = ["status"]
    fsm_field = ["status"]
    list_display = ["status",]
    fields = readonly_fields

    # because we add this parameter it will displays "turn_left" transition into CarAdmin change form
    # in addition to car start transition
    foreign_keys = ["wheel"] 

[antoinewg]

filter à supprimer du coup