packages/rum-core/src/common/utils.js
function setTag(key, value, obj) {
  if (!obj || !key) return
  var skey = removeInvalidChars(key)
  if (value) {
    value = String(value)
  }
  obj[skey] = value
  return obj
}
function setTag(key, value, obj) {
  if (!obj || !key) return
  var skey = removeInvalidChars(key)
  if (value) {
    value = String(value)
  }
  obj[skey] = value
  return obj
}
function setTag ( key , value , obj ) { if ( ! obj || ! key ) return var skey = removeInvalidChars ( key ) if ( value ) { value = String ( value ) } obj [ skey ] = value return obj }
Convert values of the tag to be string to be compatible
with the apm server prior to <6.7 version

TODO: Remove string conversion in the next major release since
support for boolean and number in the APM server has landed in 6.7
https://github.com/elastic/apm-server/pull/1712/
Convert values of the tag to be string to be compatible with the apm server prior to <6 . 7 version