As a tool developer I want to get data of descriptions of properties so I can show them in my tool.
GET /entities/properties/{property_id}/descriptions/{language_code}
**Notes**
- Request and response structures to follow what the item-related counterpart does, see https://doc.wikimedia.org/Wikibase/master/js/rest-api/#descriptions/get_entities__items___item_id__descriptions__lang_
- Handle HTTP conditional request headers as in GET /entities/items/{item_id}/descriptions/{language_code}
- Handle user authentication/authorization like in GET /entities/items/{item_id}/descriptions/{language_code}
**Error cases to consider**
<table>
<tr>
<th>
</th>
<th>HTTP response code</th>
<th>response payload</th>
</tr>
<tr>
<td>Property does not exist </td>
<td>404</td>
<td>
`"code": "property-not-found"`
`"message": "Could not find a property with the ID: {property_id}"`
</td>
</tr>
<tr>
<td>Invalid property ID </td>
<td>400</td>
<td>
`"code": "invalid-property-id"`
`"message": "Not a valid property ID: {property_id}"`
`"context": {"property": "{property-id}"}`
</td>
</tr>
<tr>
<td>Invalid language code </td>
<td>400</td>
<td>
`{ "code": "invalid-language-code", "message": "Not a valid language code: {language_code}"}`
</td>
</tr>
<tr>
<td>Property does not have descriptions in the give language </td>
<td>404</td>
<td>
`{ "code": "descriptions-not-defined", "message": "Property with the ID {property_id} does not have descriptions in the language: {language_code}" }`
</td>
</tr>
</table>
**Possibly relevant pointers:**
* Suggestion in 2020 Wikibase REST API proposal: https://wmde.github.io/wikibase-rest-api-proposal/#/descriptions/get_entities__entity_type___entity_id__descriptions__lang_
* How Wikibase Action API handles this: https://www.wikidata.org/w/api.php?action=help&modules=wbsearchentities