Investigate tenders without year

[georgiana-b]

Here is the opentender.eu dump by year:

└> ls -lah
total 38G
drwxr-xr-x 2 g users 4.0K May  1 08:35 .
drwxr-xr-x 3 g users 4.0K May  1 17:05 ..
-rw-r--r-- 1 g users 1.8G Apr 26 12:40 data-all-2009.ndjson
-rw-r--r-- 1 g users 1.9G Apr 26 12:40 data-all-2010.ndjson
-rw-r--r-- 1 g users 2.5G Apr 26 12:40 data-all-2011.ndjson
-rw-r--r-- 1 g users 2.8G Apr 26 12:40 data-all-2012.ndjson
-rw-r--r-- 1 g users 3.1G Apr 26 12:40 data-all-2013.ndjson
-rw-r--r-- 1 g users 2.9G Apr 26 12:40 data-all-2014.ndjson
-rw-r--r-- 1 g users 2.8G Apr 26 12:40 data-all-2015.ndjson
-rw-r--r-- 1 g users 2.3G Apr 26 12:40 data-all-2016.ndjson
-rw-r--r-- 1 g users 990M Apr 26 12:40 data-all-2017.ndjson
-rw-r--r-- 1 g users 524K Apr 26 12:40 data-all-2018.ndjson
-rw-r--r-- 1 g users  17G Apr 26 12:40 data-all-year-unavailable.ndjson

Notice there are a shocking 17GB of data without year. If this is true they will not appear in Elvis as it is now because they will be filtered out by year.

As @zufanka proposed:

We can just add a tickbox next to the years selector that is ticked in by default with "Include tenders with unknown publication year"

But first let's look into these more and figure how come they don't have the year and whether we can use the award year instead.