Make get_resource_sql() do a better job of tidying the SQL text

[Moohan]

I used get_resource_sql() to return some populations with the HB name, I used it because it allows me to do a join and therefore get all the data I needed as 1 API call, this is faster and was important because it was in a Shiny dashboard.

I managed to get the query to work eventually but there were a few quirks which could probably be handled internally by the function (or at the very least included in the documentation) so that users don't have to figure it out by trial and error.

hb_pop_est <- phsopendata::get_resource_sql(
    sql = paste(
      "SELECT%20pops.\"Year\", pops.\"HB\", lookup.\"HBName\", pops.\"AllAges\"",
      "FROM \"27a72cc8-d6d8-430c-8b4f-3109a9ceadb1\" pops",
      "JOIN \"652ff726-e676-4a20-abda-435b98dd7bdc\" lookup",
      "ON%20pops.\"HB\" = lookup.\"HB\"",
      "WHERE%20pops.\"Sex\" = 'All' AND%20pops.\"Year\" > 2006",
      sep = "%20"
    )
  )

From memory, I think the 'rules' are:

• Variable names must be quoted (which likely means escaping quotes) \"
• Need a space (but encoded as %20) before an after every SQL keyword unless the next bit contains quotes.

[Moohan]

Also make sure to add this to documentation.