Initial support for importing supplier costs

app/Models/Cost/Broadband.php

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+<?php
+
+namespace App\Models\Cost;
+
+use App\Models\Service;
+use App\Models\Service\Broadband as BroadbandService;
+
+class Broadband extends Type
+{
+	protected $table = 'cost_broadband';
+
+	/* RELATIONS */
+
+	public function service()
+	{
+		return $this->hasOneThrough(Service::class,BroadbandService::class,'id','id','service_broadband_id','service_id');
+	}
+}

app/Models/Cost/Generic.php

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+<?php
+
+namespace App\Models\Cost;
+
+use App\Models\Service;
+use App\Models\Service\Generic as GenericService;
+
+class Generic extends Type
+{
+	protected $table = 'cost_generic';
+
+	/* RELATIONS */
+
+	public function service()
+	{
+		return $this->hasOneThrough(Service::class,GenericService::class,'id','id','service_generic_id','service_id');
+	}
+}

app/Models/Cost/Phone.php

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+<?php
+
+namespace App\Models\Cost;
+
+use App\Models\Service;
+use App\Models\Service\Phone as PhoneService;
+
+class Phone extends Type
+{
+	protected $table = 'cost_phone';
+
+	/* RELATIONS */
+
+	public function service()
+	{
+		return $this->hasOneThrough(Service::class,PhoneService::class,'id','id','service_phone_id','service_id');
+	}
+}

app/Models/Cost/Type.php

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+<?php
+
+namespace App\Models\Cost;
+
+use Illuminate\Database\Eloquent\Model;
+
+abstract class Type extends Model
+{
+	public $timestamps = FALSE;
+
+	protected $dates = [
+		'start_at',
+		'end_at',
+	];
+
+	/* RELATIONS */
+
+	abstract public function service();
+
+	/* ATTRIBUTES */
+
+	public function getCostAttribute(): float
+	{
+		return $this->base+$this->excess;
+	}
+}