_resolvePropToValue (propertyName, value) {
    let deferred = this._promiseMap.get(propertyName)
    if (deferred == null) {
      logger.info(`[ctx] No promise found for ${String(propertyName)}`)
      deferred = this._createDeferredForProp(propertyName)
    }
    logger.info(`[ctx] Resolving promise for ${String(propertyName)}`)
    deferred.resolve(value)
  }
Gets existing promise and resolves it with the given value.

@private
@template T
@param {ContextProperties} propertyName
@param {T} value
@returns {void}