added tolower fix for capitalized col names from db

[mvankessel-EMC]

df1 is defined as:	chr_col	numeric_col
'a'	1

df2 would be fetched from SQLite as:	CHR_COL	NUMERIC_COL
'a'	1

failing the following check:

if (!isTRUE(dplyr::all_equal(df1, df2))) {
  msg <- paste("Write access to schema",
               write_schema,
               "could not be verified.")

  if (is.null(add)) {
    rlang::abort(msg)
  } else {
    add$push(msg)
  }
}

names(df2) <- tolower(names(df2))

would fix this issue, passing the check.

I verified that it would work as follows:

con <- DBI::dbConnect(
  DatabaseConnector::DatabaseConnectorDriver(),
  dbms = "sqlite",
  server = "..\\Temp\\Rtmpm8Kzj7\\file584c5526306b.sqlite")

cdm <- CDMConnector::cdmFromCon(
  con = con,
  writeSchema = "main",
  # cohortTableNames are generated by CohortGenerator.
  cohortTables = unlist(cohortTableNames))

cdm$cohort_table %>% 
  group_by(cohort_definition_id) %>% 
  tally()

Which yields:

# Source:   SQL [7 x 2]
# Database: DatabaseConnectorDbiConnection
  cohort_definition_id     n
                 <dbl> <dbl>
1                    1  2679
2                    2  2130
3                    3  1927
4                    4  2021
5                    5  1393
6                    6  1732
7                    7  2159

Which is expected.