Implement missing parameter validation

[iperdomo]

There is pending validation in request parameters for report generation, e.g.

• criteria is required and can't be null, it needs to be a valid JSON object

[qtp1625050241-31] WARN org.eclipse.jetty.server.AbstractHttpConnection - /generate?callback=FLOW.ReportLoader.handleResponse&criteria=null&_=1386827806483
java.lang.IllegalArgumentException: No implementation of method: :to-job-data of protocol: #'clojurewerkz.quartzite.conversion/JobDataMapConversion found for class: clojure.lang.PersistentList
        at clojure.core$_cache_protocol_fn.invoke(core_deftype.clj:541)
        at clojurewerkz.quartzite.conversion$fn__1633$G__1628__1638.invoke(conversion.clj:15)
        at clojurewerkz.quartzite.jobs$using_job_data.invoke(jobs.clj:57)
        at akvo.flow_services.scheduler$get_job.invoke(scheduler.clj:73)
        at akvo.flow_services.scheduler$schedule_job.invoke(scheduler.clj:82)
        at akvo.flow_services.scheduler$generate_report.invoke(scheduler.clj:118)
        at akvo.flow_services.core$generate_report.invoke(core.clj:32)
        at akvo.flow_services.core$fn__1992.invoke(core.clj:52)

[stale[bot]]

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