Add exception to status on failed job

[fmigneault]

Description

As per https://github.com/opengeospatial/ogcapi-processes/pull/399/files, the status response can now directly include the exception field.

When the job ends in status: failed, this field could be appended.
The exception details are already encoded in the job object:

weaver/weaver/datatype.py

Line 1403 in d911c16

"exceptions": self.exceptions,

Only need to add the value to the schema definition for it to be reported in the response.
Needs to consider which exception to return since a list is supported in the case of the existing job property.

References

• Add exception member. opengeospatial/ogcapi-processes#399