[Build] Enhance Xcodegen architecture

[NicolasBuquet]

Actually, the structure uses 3 xcodegen files to generate the 3 TchapX targets:

• TchapX-development : TchapX/development/SupportingFiles/target.yml
• TchapX-staging : TchapX/staging/SupportingFiles/target.yml
• TchapX-production : TchapX/staging/SupportingFiles/target.yml

The 3 target.yml files are identical except for some properties in base:settings:

    settings:
      base:
        PRODUCTION_APP_NAME: Tchap DEVELOPMENT
        BASE_APP_GROUP_IDENTIFIER: fr.gouv.tchapx.dev
        BASE_BUNDLE_IDENTIFIER: fr.gouv.tchapx.dev
        APP_NAME: TchapX-development
        APP_DISPLAY_NAME: TchapX-DEVELOPMENT
        ASSETCATALOG_COMPILER_APPICON_NAME: TchapX-icon

It should be better if these # files could be on unique template file accepting parameters:

• either via environment variables
• via a templating phase using Genesis : https://github.com/yonaskolb/Genesis (made by the author of xcodegen)

Xcodegen is not made for templating.

It is possible to use envionment variables in xcodegen:

export TCHAPX_TARGET_BASEDIR="<my custom path>"
xcodegen generate --spec tchapx-project.yml

These will replace ${TCHAPX_TARGET_BASEDIR} string with the value provided.
This means 3 calls, one for each target, or 3 set of variables for each project.

I prefer exploring Genesis path.