polish: Use `ObjectUtils#isEmpty(Object)`.

[jkschneider]

StringUtils.isEmpty was deprecated.

Co-authored-by: Moderne [email protected]

[codecov[bot]]

Codecov Report

Merging #1953 (3a84e5e) into main (401443d) will not change coverage. The diff coverage is 52.38%.

@@            Coverage Diff            @@
##               main    #1953   +/-   ##
=========================================
  Coverage     76.46%   76.46%           
  Complexity     1410     1410           
=========================================
  Files           182      182           
  Lines          5324     5324           
  Branches        704      704           
=========================================
  Hits           4071     4071           
  Misses          986      986           
  Partials        267      267           

Impacted Files	Coverage Δ
...rk/cloud/config/client/ConfigClientProperties.java	91.40% <0.00%> (ø)
...er/encryption/vault/VaultEnvironmentEncryptor.java	85.41% <0.00%> (ø)
...AwsSecretsManagerEnvironmentRepositoryFactory.java	20.00% <0.00%> (ø)
.../server/environment/JGitEnvironmentRepository.java	87.75% <0.00%> (ø)
...uthentication/PcfClientAuthenticationProvider.java	57.89% <0.00%> (ø)
...t/HttpClientConfigurableHttpConnectionFactory.java	96.87% <50.00%> (ø)
.../server/environment/JdbcEnvironmentRepository.java	69.23% <50.00%> (ø)
...server/environment/AwsS3EnvironmentRepository.java	87.05% <80.00%> (ø)
...onment/AwsSecretsManagerEnvironmentRepository.java	94.33% <100.00%> (ø)
...rver/environment/CredhubEnvironmentRepository.java	93.33% <100.00%> (ø)
... and 1 more

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