Integrating a payment application (API) in a django application - python-3.x

Question

I have a Django web application in which I would like to integrate a local payment API in order to enable customers who want to use their money from this payment application to pay their car insurance but honestly, I don't have any idea of how to do it.
Below are the related models (Contrat and Reglement):
class Contrat(models.Model):
Statut_contrat = (
('Encours', 'Encours'),
('Suspendu', 'Suspendu'),
('Expiré', 'Expiré'),
)
categorie_choices =(
('Tourisme', 'Tourisme'),
('Transport', 'Transport')
)
# numero_de_contrat = shortuuid.uuid()
type_contrat = models.ForeignKey(TypeContrat, on_delete=models.CASCADE, null=True, blank=False)
tca = models.DecimalField(_('TCA 4%'),max_digits=10, decimal_places=2, default=0.00)
numero_de_contrat = models.CharField(max_length=50, blank=True, null=True,db_index=True, unique=True)
statut_assurance =models.CharField(max_length=15, choices=Statut_contrat, default='Non')
vehicule = models.ForeignKey(Vehicule, on_delete=models.CASCADE)
utilisateur = models.ForeignKey(User, on_delete=models.CASCADE)
nombre_de_mois = models.IntegerField(null=True, blank=True)
sous_couvert = models.CharField(_('S/C'),max_length=200, null=True, blank=True)
categorie = models.CharField(max_length=50, choices=categorie_choices, null=False, blank=False, default='Tourisme')
created = models.DateField(auto_now_add=True)
modified = models.DateField(auto_now=True)
active = models.BooleanField(default=True)
remainingdays=models.IntegerField(default=0)
blocked_date=models.DateField()
unblocked_date = models.DateField(null=True, blank=True)
history = HistoricalRecords()
class Meta:
ordering=('-created',)
#property
def static_id(self):
'C{0:07d}'.format(self.pk)
def __str__(self):
return str(self.numero_de_contrat)
def save(self, *args, **kwargs):
self.tca=self.type_contrat.montant_du_contrat*Decimal(0.04)
if self.statut_assurance=="Suspendu":
dt=abs(self.blocked_date-self.modified)
print('Difference est:',dt)
numberOfDaysLeft= self.remainingdays-dt.days
print('Big diff',numberOfDaysLeft)
self.remainingdays=numberOfDaysLeft
self.blocked_date=date.today()
super(Contrat, self).save(*args, **kwargs)
def activeStatus(self):
if self.nombre_de_mois==0:
return self.active==False
else:
return self.active==True
def get_NbDays(self):
if self.statut_assurance=='Encours':
# nb_Days = timedelta(days=self.remainingdays)+date.today()
nb_Days = timedelta(days=self.remainingdays)+self.blocked_date
print('Date de fin', nb_Days)
return nb_Days
elif self.statut_assurance=='Suspendu':
nb_Days = timedelta(days=self.remainingdays) + self.blocked_date
return nb_Days
else:
nb_Days = self.modified
return nb_Days
class Reglement(models.Model):
payment_list = (('Espece', 'Espece'),
('Cheque', 'Cheque'),
('Carte de crédit', 'Carte de crédit'),
('Carte de débit', 'Carte de débit'),
('A crédit', 'A crédit'),)
code_reglement = models.CharField(max_length=50, blank=True, null=True, db_index=True, unique=True)
contrat = models.ForeignKey(Contrat, on_delete=models.CASCADE)
utilisateur = models.ForeignKey(User, on_delete=models.CASCADE)
date_reglement = models.DateField(auto_now_add=True)
montant_a_regler = models.DecimalField(max_digits=10, decimal_places=2)
mode_de_paiment = models.CharField(max_length=15,choices=payment_list)
created = models.DateField(auto_now_add=True)
modified = models.DateField(auto_now=True)
regle = models.BooleanField(default=False)
history = HistoricalRecords()
class Meta:
ordering=('-created',)
#property
def static_id(self):
'R{0:07d}'.format(self.pk)
Please assist me