code: public static String replaceOnceIgnoreCase(final String text, final String searchString, final String replacement) {
          return replaceIgnoreCase(text, searchString, replacement, 1);
      }
docs: <p>Case insensitively replaces a String with another String inside a larger String, once.</p>
  
  <p>A {@code null} reference passed to this method is a no-op.</p>
  
  <pre>
  StringUtils.replaceOnceIgnoreCase(null, *, *)        = null
  StringUtils.replaceOnceIgnoreCase("", *, *)          = ""
  StringUtils.replaceOnceIgnoreCase("any", null, *)    = "any"
  StringUtils.replaceOnceIgnoreCase("any", *, null)    = "any"
  StringUtils.replaceOnceIgnoreCase("any", "", *)      = "any"
  StringUtils.replaceOnceIgnoreCase("aba", "a", null)  = "aba"
  StringUtils.replaceOnceIgnoreCase("aba", "a", "")    = "ba"
  StringUtils.replaceOnceIgnoreCase("aba", "a", "z")   = "zba"
  StringUtils.replaceOnceIgnoreCase("FoOFoofoo", "foo", "") = "Foofoo"
  </pre>
  
  @see #replaceIgnoreCase(String text, String searchString, String replacement, int max)
  @param text  text to search and replace in, may be null
  @param searchString  the String to search for (case insensitive), may be null
  @param replacement  the String to replace with, may be null
  @return the text with any replacements processed,
  {@code null} if null String input
  @since 3.5