title: Check if coordinates are on the boundary of a feature in OL
body: <p>I am using OpenLayers 5 <a href="https://openlayers.org/" rel="nofollow noreferrer">https://openlayers.org/</a> and cannot find a solution how to check if given coordinates are on the boundary of a feature.</p>
  
  <p>I played with <code>map.getFeaturesAtPixel</code> and <code>geometry.intersectsCoordinate</code>, but there is always the problem that the functions also return true if the coordinates are IN the feature. I only want the result to be true if the coordinates are ON the boundary of the feature.</p>
  
  <p>Background: The user can draw lines on a map and connect them with other features (therefore I use <code>ol.interaction.Snap</code>). When saving I want to have the features which were 'snapped' bei the user. I cannot find an event or something else what tells me what features where snapped. Therefore I was trying to find a solution to self extract the features which are connected to the new line, but nothing works.</p>
  
  <p>I hope the picture makes it clear. The user draws the new line (blue), the line snaps in the two polygones. After drawing the line, I want to read the two features.</p>
  
  <p>Any help is welcome!</p>
  
  <p><a href="https://i.stack.imgur.com/40asu.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/40asu.png" alt="enter image description here"></a></p>