feat: allow disabling automatic version detection for releases

[jakub300]

This small change allows release to be set to undefined without being overridden with automatic release.

In v4 it was possible to set clientConfig: { release: undefined } (and same for server) to override automatically generated value. In v5 the merging library has been changed to lodash.merge which is ignoring undefined values making it no longer possible to override automatic release generation.

We prefer not to include release in the configuration to avoid unnecessary changes to built files (small perf improvement for returning visitors). Instead we rely on window.SENTRY_RELEASE/process.env.SENTRY_RELEASE. For that to work release must be undefined.

[codecov]

Codecov Report

Merging #314 (3d64204) into master (9e3ae22) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #314   +/-   ##
=======================================
  Coverage   55.55%   55.55%           
=======================================
  Files           1        1           
  Lines          27       27           
  Branches        8        8           
=======================================
  Hits           15       15           
  Misses          9        9           
  Partials        3        3           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9e3ae22...3d64204. Read the comment docs.