Function mergeConfigs

mergeConfigs(...sources: Partial<InstallConfig>[]): PartialInstallConfig
Merge multiple partial configs into one. Later sources override earlier ones.

Only fields that are explicitly present (not undefined) in a source override the corresponding field from earlier sources. The AuthProviderValues record is shallow-merged (keys from later sources override keys from earlier sources, but unmentioned keys are preserved).
Parameters
- ...sources: Partial<InstallConfig>[]
  Partial configs in priority order (lowest first).
Returns PartialInstallConfig
A single merged partial config.
Example
```
const merged = mergeConfigs(
  InstallConfigDefaults,          // lowest priority
  resolveFromEnvironment(),       // env vars override defaults
  await loadConfigFile('c.json'), // file overrides env vars
  runOptions.Config ?? {},        // CLI overrides file
);
```
- Defined in packages/MJInstaller/src/models/InstallConfig.ts:507