refactor: strategy pattern for deckfile fetching

[buschNT]

• preparation for bugfixes + features regarding deckfile, e.g. Support relative file system paths when Deckfile is loaded via Git #81
• decouple deckfile fetching from parsing
• tests added

[coveralls]

Pull Request Test Coverage Report for Build 3205915364

• 92 of 150 (61.33%) changed or added relevant lines in 9 files are covered.
• 7 unchanged lines in 6 files lost coverage.
• Overall coverage increased (+0.5%) to 63.579%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
getdeck/api/hosts.py	1	2	50.0%
getdeck/api/list.py	1	2	50.0%
getdeck/api/remove.py	2	3	66.67%
getdeck/utils.py	17	23	73.91%
getdeck/deckfile/fetch/utils.py	4	19	21.05%
getdeck/deckfile/fetch/deck_fetcher.py	58	92	63.04%

Files with Coverage Reduction	New Missed Lines	%
getdeck/api/get.py	1	71.43%
getdeck/api/hosts.py	1	31.11%
getdeck/api/list.py	1	56.25%
getdeck/api/stop.py	1	93.75%
getdeck/utils.py	1	58.79%
getdeck/api/remove.py	2	30.51%

Totals
Change from base Build 3152532040:	0.5%
Covered Lines:	1201
Relevant Lines:	1889

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💛 - Coveralls

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
12 Code Smells

No Coverage information
0.0% Duplication