Add support for expressions in endpoint definition attributes.

[chathuranga-jayanath-99]

Purpose

Consider the following HTTP endpoint definition. To handle this definition, expression support is required for endpoint attributes. Currently, only timeout-duration supports expressions, but the need for expression support in other attributes has occurred during the implementation of the HTTP connector.

<http method="get" uri-template="{uri.var.base}{+uri.var.path}{+uri.var.query}">
  <timeout>
      <duration>{get-property('timeoutDuration')}</duration>
      <responseAction>{get-property('timeoutAction')}</responseAction>
  </timeout>
  <suspendOnFailure>
      <errorCodes>{get-property('suspendErrorCodes')}</errorCodes>
      <initialDuration>{get-property('suspendInitialDuration')}</initialDuration>
      <maximumDuration>{get-property('suspendMaximumDuration')}</maximumDuration>
      <progressionFactor>{get-property('suspendProgressionFactor')}</progressionFactor>
  </suspendOnFailure>
  <markForSuspension>
      <errorCodes>{get-property('retryErrorCodes')}</errorCodes>
      <retriesBeforeSuspension>{get-property('retryCount')}</retriesBeforeSuspension>
      <retryDelay>{get-property('retryDelay')}</retryDelay>
  </markForSuspension>
</http>

[GDLMadushanka]

Please squash these commits to a single one

[SanojPunchihewa]

Do we need this check? The ValueFactory will check wether it's an expression or not and resolve the value.

[chathuranga-jayanath-99]

Updated using ValueFactory.