Fixed values when creating fieldmaps

When creating fieldmaps Ive almost always had to create hidden fields for nodes or webform submissions in order to pass static data to Salesforce (ie object ids, static text). Although this method works fine duplicating data for each node/submission is far from ideal. Also the process of adding a hidden field is outside of the fieldmap creation process, instead its done using the admin content type pages, webform config page.....etc. This complicates the setup process for site admins.

Ive created a patch that adds an additional 'Fixed value' option to each of the source select boxes on the fieldmap add/edit page. When the site admin selects the fixed value option a hidden text field next to the select box is revealed using js, this field can be used to enter a static value that is used when exporting data.

The patch alters the fieldmap definition array so that fields with a fixed value become an array with 'type' and 'value' keys. When Drupal creates the object for export if the fieldmap definition contains a field with type = 'fixed' then the static value is used.

If people think is a useful feature then the idea could be extended further to include a Salesforce ID look up for the static data.
eg
1. site admin click 'sf lookup' link next fixed value textfield
2. a popup presents a form where the user can view a list of all salesforce objects filtered by type
3. user clicks on the Salesforce object they want to use as the fixed value
4. the popup closes and the textfield is autopopulated with the ID of the selected Salesforce object.

To apply the patch use the "-p0" option (eg patch -p0 < salesforce_api_xxxxxx.patch) to avoid having to confirm filepaths.

Thoughts, feedback, bugs are welcome....