Migrates to Pester5+ tests (#59)

#### 📖 Summary

- update Pester tests to Pester5+ compatiple layout
- switch to dotnet base imaged
  - dotnet binary required for publishung powershell modules (Publish-Module)

#### 📑 Test Plan

> 💡 Select your test plan for the code changes.

- [x] Tested via Drone.io pipeline
- [ ] Custom test
- [ ] No test plan

##### Details / Justification

<!-- Add your test details or justification for missing tests here. -->

#### 📚 Additional Notes

<!-- A place for additional detail notes. -->

Co-authored-by: OCram85 <marco.blessing@googlemail.com>
Reviewed-on: OCram85/PSCredentialStore#59

src/Private/Get-DefaultCredentialStorePath.Tests.ps1

@@ -0,0 +1,62 @@
+BeforeAll {
+    $ManifestFile = (Get-Item -Path "./src/*.psd1").FullName
+    Import-Module $ManifestFile -Force
+
+    $PrivateFunctions = (Get-ChildItem -Path "./src/Private/*.ps1" | Where-Object {
+            $_.BaseName -notmatch '.Tests'
+        }
+    ).FullName
+    foreach ( $func in $PrivateFunctions) {
+        . $func
+    }
+}
+
+Describe "Get-DefaultCredentialStorePath" {
+    Context "Basic syntax test" {
+        It "Test1: Should not throw" {
+            { Get-DefaultCredentialStorePath } | Should -Not -Throw
+        }
+    }
+
+    Context "Private Type" {
+        It "Should return correct paths" {
+            $Path = Get-DefaultCredentialStorePath
+            #Write-Verbose -Message ('Delivered path is: {0}' -f $Path) -Verbose
+            if ($Env:APPVEYOR) {
+                $PathRef = Join-Path -Path $Env:APPDATA -ChildPath 'CredentialStore.json'
+                $Path | Should -Be $PathRef
+            }
+            elseif ($ENV:TRAVIS) {
+                if ($IsLinux) {
+                    $PathRef = Join-Path -Path $Env:HOME -ChildPath 'CredentialStore.json'
+                    $Path | Should -Be $PathRef
+                }
+                elseif ($IsMacOS) {
+                    $PathRef = Join-Path -Path $Env:HOME -ChildPath 'CredentialStore.json'
+                    $Path | Should -Be $PathRef
+                }
+            }
+        }
+    }
+
+    Context "Shared Type" {
+        It "Should return correct paths" {
+            $Path = Get-DefaultCredentialStorePath -Shared
+            #Write-Verbose -Message ('Delivered path is: {0}' -f $Path) -Verbose
+            if ($Env:APPVEYOR) {
+                $PathRef = Join-Path -Path $env:ProgramData -ChildPath 'PSCredentialStore/CredentialStore.json'
+                $Path | Should -Be $PathRef
+            }
+            elseif ($ENV:TRAVIS) {
+                if ($IsLinux) {
+                    $PathRef = Join-Path -Path '/var/opt' -ChildPath 'PSCredentialStore/CredentialStore.json'
+                    $Path | Should -Be $PathRef
+                }
+                elseif ($IsMacOS) {
+                    $PathRef = Join-Path -Path '/var/opt' -ChildPath 'PSCredentialStore/CredentialStore.json'
+                    $Path | Should -Be $PathRef
+                }
+            }
+        }
+    }
+}