Send email with results of pretest in case all DOIs were not accepted

[njahn82]

An email should be send to the users when DOIs do not meet eligible criteria. The email ideally contains a report and the data attachment.

Example

library(metacheck)
miss_dois <- c("10.1016/B978-0-12-803581-8.12084-3",
               "10.1515/9783110438321-201",
               "10.1007/978-3-030-30978-7",
               "10.1007/978-3-030-20867-7",
               "10.1007/978-3-319-74989-1_7",
               "10.5281/ZENODO.3474968",
               "10.5281/ZENODO.3489385",
               "10.5281/ZENODO.3666686",
               "10.5281/ZENODO.3674003",
               "10.5281/ZENODO.3763313",
               "10.5281/ZENODO.3982290",
               "10.2312/ESKP.2020.2.7.5",
               "10.2312/IASS.2020.037",
               "10.1007/978-3-662-48297-1",
               "10.1142/9789811202339_0003",
               "10.5281/ZENODO.4382017")
tabulate_metacheckable(miss_dois)
#> # A tibble: 16 x 7
#>    not_missing unique within_limits doi_org_found from_cr cr_md article
#>    <lgl>       <lgl>  <lgl>         <lgl>         <lgl>   <lgl> <lgl>  
#>  1 TRUE        TRUE   TRUE          TRUE          TRUE    TRUE  FALSE  
#>  2 TRUE        TRUE   TRUE          TRUE          TRUE    TRUE  FALSE  
#>  3 TRUE        TRUE   TRUE          TRUE          TRUE    TRUE  FALSE  
#>  4 TRUE        TRUE   TRUE          TRUE          TRUE    TRUE  FALSE  
#>  5 TRUE        TRUE   TRUE          TRUE          TRUE    TRUE  FALSE  
#>  6 TRUE        TRUE   TRUE          TRUE          FALSE   NA    NA     
#>  7 TRUE        TRUE   TRUE          TRUE          FALSE   NA    NA     
#>  8 TRUE        TRUE   TRUE          TRUE          FALSE   NA    NA     
#>  9 TRUE        TRUE   TRUE          TRUE          FALSE   NA    NA     
#> 10 TRUE        TRUE   TRUE          TRUE          FALSE   NA    NA     
#> 11 TRUE        TRUE   TRUE          TRUE          FALSE   NA    NA     
#> 12 TRUE        TRUE   TRUE          TRUE          FALSE   NA    NA     
#> 13 TRUE        TRUE   TRUE          TRUE          FALSE   NA    NA     
#> 14 TRUE        TRUE   TRUE          TRUE          TRUE    TRUE  FALSE  
#> 15 TRUE        TRUE   TRUE          TRUE          TRUE    TRUE  FALSE  
#> 16 TRUE        TRUE   TRUE          TRUE          FALSE   NA    NA

^{Created on 2021-03-22 by the reprex package (v0.3.0)}

[maxheld83]

closing in favor of #285; no DOIs left after pretest is a special case of #285.
Will also be tested in #279