Fix KubeConfig temp certificate filename extension .pem

[stefankonig]

With the merging of #182 i think an unintentional bug was introduced in the temp certificate filename. The $fileName is included in the Str::slug function parameter, causing the certificate filename to lose the dot of the file extension.

before: ctx-minikube-ca-cert.pem
now: ctx-minikube-minikube-httpsminikube8443-ca-certpem
after fix: ctx-minikube-minikube-httpsminikube8443-ca-cert.pem

i have additionally added a few extra assertions to the test_kube_config_from_yaml_file_with_base64_encoded_ssl unittest to check the generated filename.

[codecov]

Codecov Report

Merging #186 (236a771) into master (990acd6) will increase coverage by 0.12%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master     #186      +/-   ##
============================================
+ Coverage     95.09%   95.22%   +0.12%     
  Complexity      694      694              
============================================
  Files            70       70              
  Lines          1693     1696       +3     
============================================
+ Hits           1610     1615       +5     
+ Misses           83       81       -2     

Impacted Files	Coverage Δ
src/Traits/Cluster/LoadsFromKubeConfig.php	94.31% <100.00%> (ø)
src/Traits/Cluster/MakesWebsocketCalls.php	89.74% <0.00%> (+0.41%)	⬆️
src/Kinds/K8sPod.php	95.93% <0.00%> (+1.62%)	⬆️

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[rennokki]

Thank you. <3 I usually rely on tests for these, it seems like this was missing. 😁