HomoCodens

It appears x13 does not write the `.est` file under certain conditions and `seasonal` attempts to read it without any checks. Should be pretty straight forward to fix in https://github.com/christophsax/seasonal/blob/main/R/read_est.R#L8...

Resolve conflicts and merge as discussed with @mbannert

Let's move the check: ``` tsl

And while we're at it add a check that valid_on is a date vector of length 1.

The problem was that RPostgres 1.4.3 adds type casts in `dbQuoteLiteral` so `dbQuoteLiteral(con, NA)` becomes `NULL:bool` instead of the previous `NULL`.

also some other "diagnostic" information would be helpful too: * start * end * first/last value * frequency * created at * created by * etc.

exactly. It's not critical for timeseriesdb to function so I classified it as "maintenance" in my mind.

Actually, it may now _have_ to be a `Date` at least when it is passed to `dbQuoteLiteral`. See #250. Currently it is documented thusly: ``` #' @param valid_on \strong{character} representation...

this is probably already in use somewhere so such a change would fall under "breaking changes" on the other hand a 1 column data.frame is basically a vector and it...

check for consistency with e.g. listing keys in dataset