title: Set the right crs on sf object to plot coordinate points
body: <p>I'm trying to define the right CRS for my <code>sf</code> object. I want to plot points atop the following layer (country: the Netherlands):</p>
  
  <pre><code>Simple feature collection with 380 features and 3 fields
  geometry type:  MULTIPOLYGON
  dimension:      XY
  bbox:           xmin: 13565.4 ymin: 306846.2 xmax: 278026.1 ymax: 619232.6
  epsg (SRID):    NA
  proj4string:    +proj=sterea +lat_0=52.15616055555555 +lon_0=5.38763888888889 +k=0.9999079 +x_0=155000 +y_0=463000 +ellps=bessel +units=m +no_defs
  </code></pre>
  
  <p>output:</p>
  
  <p><img src="https://i.stack.imgur.com/4aEqE.png" alt="enter image description here"></p>
  
  <p>This layer has the correct projection.</p>
  
  <p>But the <code>POINT</code> layer doesn't have the correct CRS project presumably because it has no <code>proj4string</code>?</p>
  
  <pre><code>Simple feature collection with 566 features and 5 fields
  geometry type:  POINT
  dimension:      XY
  bbox:           xmin: 3.5837 ymin: 50.86487 xmax: 7.120998 ymax: 53.44835
  epsg (SRID):    NA
  proj4string:    NA
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/AoIun.png" alt="enter image description here"></p>
  
  <p>How do I set the same projection as the previous map so I can plot the coordinates points on it?</p>