Poor handling when observation_code does not exist in inpatient_investigations

[peterdutey]

clinical_feature_*() functions produce hard to read error messages.
When chaining several functions the message become very long and truncates the useful part.

Current behaviour

> clinical_feature_last(
+     TherapyEpisode(conSQLite, "4d611fc8886c23ab047ad5f74e5080d7"),
+     observation_code = "doesnotexist",
+     hours = 24
+ )
Error in .clinical_investigation_code_validate(conn = x@conn, observation_code = observation_code,  : 
  Some `observation_code` were not found in the database: 'doesnotexist'

chaining:

>   clinical_feature_last(
+     TherapyEpisode(conSQLite, "4d611fc8886c23ab047ad5f74e5080d7"),
+     observation_code = "doesnotexist",
+     hours = 24
+   ) %>% 
+     clinical_feature_last(
+       TherapyEpisode(conSQLite, "4d611fc8886c23ab047ad5f74e5080d7"),
+       observation_code = "8310-5",
+       hours = 24
+     )
Error in h(simpleError(msg, call)) : 
  error in evaluating the argument 'x' in selecting a method for function 'clinical_feature_last': Some `observation_code` were not found in the database: 'doesnotexist'

Desired behaviour

> clinical_feature_last(
+     TherapyEpisode(conSQLite, "4d611fc8886c23ab047ad5f74e5080d7"),
+     observation_code = "doesnotexist",
+     hours = 24
+ )
Error: Some `observation_code` were not found in the database: 'doesnotexist'

chaining:

>   clinical_feature_last(
+     TherapyEpisode(conSQLite, "4d611fc8886c23ab047ad5f74e5080d7"),
+     observation_code = "doesnotexist",
+     hours = 24
+   ) %>% 
+     clinical_feature_last(
+       TherapyEpisode(conSQLite, "4d611fc8886c23ab047ad5f74e5080d7"),
+       observation_code = "8310-5",
+       hours = 24
+     )
Error: Some `observation_code` were not found in the database: 'doesnotexist'

[peterdutey]

Related to https://stackoverflow.com/questions/62327810/inconsistent-error-handling-of-function-and-s4-generics-on-r-4-0-1