Add ERG/BTC Datapoint Sources

[coveralls]

Pull Request Test Coverage Report for Build 5622633856

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 46 unchanged lines in 8 files lost coverage.
• Overall coverage increased (+0.1%) to 54.633%

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Files with Coverage Reduction	New Missed Lines	%
core/src/datapoint_source/erg_xau.rs	2	66.67%
core/src/datapoint_source/assets_exchange_rate.rs	4	50.0%
core/src/datapoint_source.rs	5	0%
core/src/datapoint_source/coingecko.rs	6	70.73%
core/src/pool_config.rs	6	66.67%
core/src/datapoint_source/bitpanda.rs	7	62.96%
core/src/datapoint_source/coincap.rs	7	62.96%
core/src/datapoint_source/predef.rs	9	0%
<!--	Total:	46		-->

Totals
Change from base Build 5596499533:	0.1%
Covered Lines:	2093
Relevant Lines:	3831

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💛 - Coveralls