LP#2097281: Fix for last_captured_hold Item link

A new source, alhr (action.last_hold_request), was created in commit
5b4b700 and was linked from the item table (asset.copy).
Unfortunately, there was a misunderstanding about what the various
reltype values are used for, and the incorrect one was used here.

This commit changes the reltype to "might_have" so that the correct SQL
joins can be created by the reporter, and so that fleshing requests for
this field can be performed correctly by the C-based storage services.

Reports based on this link from Item (acp) to Last Captured Hold (alhr)
will have to be recreated, as the reltype value is used to build the
core template join tree.

For reference, the three reltype values and their uses are:

 * has_a - the field on the class holding the link is backed by an
   actual column on class's the table.  There is only every one object
   present through "has_a" linked fields.
 * has_many - the field on the class (the local class) holding the link
   is a virtual field, is not backed by an actual column on the table,
   but instead describes a relationship where the foreign class holds a
   field (and has a real table column) that points back to this class
   using the primary key value of the specific, local object. There can
   be multiple foreign objects pointing to the local object, and
   therefore the data is always represented as an array when fleshed.
 * might_have - just like "has_many", where the field on the local class
   is not backed by an actual table column, but instead the foreign
   class points to it using the local primary key.  Unlike "has_many",
   there will only every be one foreign object pointing to the local
   object, so when fleshed the content of the virtual field is never an
   array of objects, but either one specific object or NULL.

To test:
 1) Attempt to run a report based on a template that goes through the
    last_captured_hold link
 2) See that it fails due to a join on a column that does not exist.
 2) Fully install the updated IDL
 3) Repeat (1); see that the report does not fail

Release-note: Fixes reporting source Item's link for last captured hold

Co-authored-by: Steven Callender <[email protected]>
Signed-off-by: Steven Callender <[email protected]>
Signed-off-by: Mike Rylander <[email protected]>
Signed-off-by: Galen Charlton <[email protected]>

Author: 2 people

Open-ILS/examples/fm_IDL.xml

@@ -8240,7 +8240,7 @@ SELECT  usr,
 			<link field="parts" reltype="has_many" key="target_copy" map="part" class="acpm"/>
 			<link field="peer_record_maps" reltype="has_many" key="target_copy" map="" class="bpbcm"/>
 			<link field="peer_records" reltype="has_many" key="target_copy" map="peer_record" class="bpbcm"/>
-			<link field="last_captured_hold" reltype="has_a" key="current_copy" map="" class="alhr"/>
+			<link field="last_captured_hold" reltype="might_have" key="current_copy" map="" class="alhr"/>
 			<link field="latest_inventory" reltype="might_have" key="copy" map="" class="alci"/>
 			<link field="copy_inventory" reltype="might_have" key="copy" map="" class="aci"/>
 			<link field="floating" reltype="has_a" key="id" map="" class="cfg"/>