Decode `.bpchar` as `String`

[gwynne]

bpchar is "blank-padded char", the low-level Postgres name for character(N) (the auto-padded form of character varying). String's PostgresCodable conformance should thus recognize it as a valid representation.

[codecov-commenter]

Codecov Report

Merging #368 (670f66a) into main (b3e1881) will increase coverage by 0.00%. The diff coverage is 100.00%.

:exclamation: Current head 670f66a differs from pull request most recent head 19dbc08. Consider uploading reports for the commit 19dbc08 to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #368 +/- ## ======================================= Coverage 42.97% 42.98% ======================================= Files 118 118 Lines 8242 8243 +1 ======================================= + Hits 3542 3543 +1 Misses 4700 4700 ``` | [Impacted Files](https://app.codecov.io/gh/vapor/postgres-nio/pull/368?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vapor) | Coverage Δ | | |---|---|---| | [.../PostgresNIO/New/Data/String+PostgresCodable.swift](https://app.codecov.io/gh/vapor/postgres-nio/pull/368?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vapor#diff-U291cmNlcy9Qb3N0Z3Jlc05JTy9OZXcvRGF0YS9TdHJpbmcrUG9zdGdyZXNDb2RhYmxlLnN3aWZ0) | `100.00% <100.00%> (ø)` | |

[michal-tomlein]

Any chance this could be released soon? We would like to get the CVE fix, but this broke our app. Thanks!

[gwynne]

@michal-tomlein We just released 1.15.0, which includes this fix, thanks for the nudge! ❤️