MDL-55030 core: Support min and max in axes

Part of MDL-54987 epic.

lib/classes/chart_axis.php

@@ -45,6 +45,8 @@ class chart_axis implements JsonSerializable {
     const POS_TOP = 'top';
 
     protected $label = null;
+    protected $max = null;
+    protected $min = null;
     protected $position = self::POS_DEFAULT;
     protected $stepsize = null;
 
@@ -55,6 +57,14 @@ class chart_axis implements JsonSerializable {
         return $this->label;
     }
 
+    public function get_max() {
+        return $this->max;
+    }
+
+    public function get_min() {
+        return $this->min;
+    }
+
     public function get_position() {
         return $this->position;
     }
@@ -66,6 +76,8 @@ class chart_axis implements JsonSerializable {
     public function jsonSerialize() {
         return [
             'label' => $this->label,
+            'max' => $this->max,
+            'min' => $this->min,
             'position' => $this->position,
             'stepSize' => $this->stepsize,
         ];
@@ -75,6 +87,14 @@ class chart_axis implements JsonSerializable {
         return $this->label = $label;
     }
 
+    public function set_max($max) {
+        return $this->max = $max;
+    }
+
+    public function set_min($min) {
+        return $this->min = $min;
+    }
+
     public function set_position($position) {
         return $this->position = $position;
     }