feat: add Invokable scripts API

[bednar]

Proposed Changes

1. Added API for InvokableScripts.
2. Changed supported InfluxDB version from InfluxDB 2.0 to InfluxDB 2.x

Checklist

• [x] CHANGELOG.md updated
• [x] Rebased/mergeable
• [x] A test has been added if appropriate
• [x] swift test completes successfully
• [x] Commit messages are in semantic format
• [x] Sign CLA (if not already signed)

[codecov-commenter]

Codecov Report

Merging #48 (5f50cff) into master (2d4ce6e) will decrease coverage by 14.42%. The diff coverage is 22.72%.

@@             Coverage Diff             @@
##           master      #48       +/-   ##
===========================================
- Coverage   80.54%   66.11%   -14.43%     
===========================================
  Files          10       16        +6     
  Lines        1033     1278      +245     
===========================================
+ Hits          832      845       +13     
- Misses        201      433      +232     

Impacted Files	Coverage Δ
...ources/InfluxDBSwift/Generated/Models/Script.swift	0.00% <0.00%> (ø)
...DBSwift/Generated/Models/ScriptCreateRequest.swift	0.00% <0.00%> (ø)
...wift/Generated/Models/ScriptInvocationParams.swift	0.00% <0.00%> (ø)
...DBSwift/Generated/Models/ScriptUpdateRequest.swift	0.00% <0.00%> (ø)
...urces/InfluxDBSwift/Generated/Models/Scripts.swift	0.00% <0.00%> (ø)
Sources/InfluxDBSwift/InvokableScriptsAPI.swift	0.00% <0.00%> (ø)
Sources/InfluxDBSwift/QueryAPI.swift	64.42% <64.70%> (-5.98%)	:arrow_down:
Sources/InfluxDBSwift/InfluxDBClient.swift	82.75% <82.60%> (-1.19%)	:arrow_down:
Sources/InfluxDBSwift/FluxCSVParser.swift	94.85% <89.47%> (-1.34%)	:arrow_down:
Sources/InfluxDBSwift/DeleteAPI.swift	79.72% <100.00%> (+0.27%)	:arrow_up:
... and 1 more

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[bednar]

@rhajek this PR depends on #49