Improve error message with not working search services

[offtherailz]

Description

If we create a new search service in mapstore and, for instance, the error is not clear. We should try to parse the error to identify if it is an xml error, before rising the parse exception, an extract the more precise error from XML error

Acceptance criteria

• if we insert a search service in mapstore with a layer, for instance that doesn't exist, the error should be clearly "Feature type unknown" as reported in the error

  <ows:Exception exceptionCode="InvalidParameterValue" locator="typeName">
    <ows:ExceptionText>Feature type gs:us_states1 unknown</ows:ExceptionText>
  </ows:Exception>
</ows:ExceptionReport> ```
If couldn't find the exception text, rise the original error.


## Other useful information
<!-- error stack trace, screenshot, videos, or link to repository code are welcome -->