Modify `Styleable` to avoid using static inline styles

To prevent CSP violation the following changes has been made in `Styleable::class`:
1) `Styleable::getStyle()` method is modified to return `ipl\Web\Style::class`
2) `Styleable::additionalStyle` property type is changed to array
3) `Styleable::setAdditionalStyle()` parameter type is changed to array

library/Icinga/Chart/Graph/BarGraph.php

@@ -112,7 +112,7 @@ class BarGraph extends Styleable implements Drawable
             $rect->setAttribute('data-icinga-graph-index', $index);
         }
         $rect->setAttribute('data-icinga-graph-type', 'bar');
-        $rect->setAdditionalStyle('clip-path: url(#clip);');
+        $rect->setAdditionalStyle(['clip-path' => 'url(#clip)']);
         return $rect;
     }
 

library/Icinga/Chart/Graph/LineGraph.php

@@ -165,8 +165,8 @@ class LineGraph extends Styleable implements Drawable
             $path->setFill($this->fill);
         }
 
-        $path->setAdditionalStyle('clip-path: url(#clip);');
-        $path->setId($this->id);
+        $path->setAdditionalStyle(['clip-path' => 'url(#clip)']);
+        $path->setId($this->id ?? uniqid('line-graph-'));
         $group = $path->toSvg($ctx);
 
         foreach ($this->dataset as $x => $point) {
@@ -180,7 +180,7 @@ class LineGraph extends Styleable implements Drawable
             if (isset($this->tooltips[$x])) {
                 $invisible = new Circle($point[0], $point[1], 20);
                 $invisible->setFill($this->strokeColor);
-                $invisible->setAdditionalStyle('opacity: 0.0;');
+                $invisible->setAdditionalStyle(['opacity' => '0.0']);
                 $data = array(
                     'label' => isset($this->graphs[$this->order]['label']) ?
                             strtolower($this->graphs[$this->order]['label']) : '',

library/Icinga/Chart/Primitive/Styleable.php

@@ -5,6 +5,8 @@
 namespace Icinga\Chart\Primitive;
 
 use DOMElement;
+use Icinga\Util\Csp;
+use ipl\Web\Style;
 
 /**
  * Base class for stylable drawables
@@ -36,14 +38,14 @@ class Styleable
     /**
      * Additional styles to be appended to the style attribute
      *
-     * @var string
+     * @var array<string, string>
      */
-    public $additionalStyle = '';
+    public $additionalStyle = [];
 
     /**
      * The id of this element
      *
-     * @var string
+     * @var ?string
      */
     public $id = null;
 
@@ -83,7 +85,7 @@ class Styleable
     /**
      * Set additional styles for this drawable
      *
-     * @param   string $styles  The styles to set additionally
+     * @param   array<string, string> $styles  The styles to set additionally
      *
      * @return  $this            Fluid interface
      */
@@ -121,15 +123,20 @@ class Styleable
     }
 
     /**
-     * Return the content of the style attribute as a string
+     * Return the ruleset used for styling the DOMNode
      *
-     * @return string A string containing styles
+     * @return Style A ruleset containing styles
      */
     public function getStyle()
     {
-        $base = sprintf("fill: %s; stroke: %s;stroke-width: %s;", $this->fill, $this->strokeColor, $this->strokeWidth);
-        $base .= ';' . $this->additionalStyle . ';';
-        return $base;
+        $styles = $this->additionalStyle;
+        $styles['fill'] = $this->fill;
+        $styles['stroke'] = $this->strokeColor;
+        $styles['stroke-width'] = (string) $this->strokeWidth;
+
+        return (new Style())
+            ->setNonce(Csp::getStyleNonce())
+            ->add("#$this->id", $styles);
     }
 
     /**