fix: squash base config with mapstructure

[sweatybridge]

What kind of change does this PR introduce?

Bug fix #2772

What is the new behavior?

For future reference, the order of loading env var to config is

1. cobra loads cli flags to viper with automatic env
2. godotenv loads .env / .env.local / .env.development files
3. mapstructure dumps default config struct to map
4. viper loads from config map (4) with automatic env (3)
5. viper dumps its state back to config

Additional context

We can potentially remove dependency on godotenv by having viper load from .env files.

[coveralls]

Pull Request Test Coverage Report for Build 11389178479

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 1 (0.0%) changed or added relevant line in 1 file are covered.
• 5 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.03%) to 59.748%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
cmd/root.go	0	1	0.0%

Files with Coverage Reduction	New Missed Lines	%
internal/gen/keys/keys.go	5	12.9%

Totals
Change from base Build 11362162748:	0.03%
Covered Lines:	6356
Relevant Lines:	10638

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💛 - Coveralls