Laravel 5.8 is not supported

[lukacavic]

Problem 1
- Installation request for oanhnn/laravel-pricing-plans ^0.3.3 -> satisfiable by oanhnn/laravel-pricing-plans[v0.3.3].
- Conclusion: remove nesbot/carbon 2.21.3
- Conclusion: don't install nesbot/carbon 2.21.3
- oanhnn/laravel-pricing-plans v0.3.3 requires nesbot/carbon ~1.21 -> satisfiable by nesbot/carbon[1.21.0, 1.22.0, 1.22.1, 1.23.0, 1.24.0, 1.24.1, 1.24.2, 1.25.0, 1.25.1, 1.25.3, 1.26.0, 1.26.1, 1.26.2, 1.26.3, 1.26.4, 1.26.5, 1.26.6, 1.27.0, 1.28.0, 1.29.0, 1.29.1, 1.29.2, 1.30.0, 1.31.0, 1.31.1, 1.32.0, 1.33.0, 1.34.0, 1.34.1, 1.34.2, 1.34.3, 1.34.4, 1.35.0, 1.35.1, 1.36.0, 1.36.1, 1.36.2, 1.37.0, 1.37.1, 1.38.0, 1.38.1, 1.38.2, 1.38.3, 1.38.4, 1.39.0].
- Can only install one of: nesbot/carbon[1.26.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.26.1, 2.21.3].
- Can only install one of: nesbot/carbon[1.26.2, 2.21.3].
- Can only install one of: nesbot/carbon[1.26.3, 2.21.3].
- Can only install one of: nesbot/carbon[1.26.4, 2.21.3].
- Can only install one of: nesbot/carbon[1.26.5, 2.21.3].
- Can only install one of: nesbot/carbon[1.26.6, 2.21.3].
- Can only install one of: nesbot/carbon[1.27.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.28.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.29.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.29.1, 2.21.3].
- Can only install one of: nesbot/carbon[1.29.2, 2.21.3].
- Can only install one of: nesbot/carbon[1.30.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.31.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.31.1, 2.21.3].
- Can only install one of: nesbot/carbon[1.32.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.33.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.34.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.34.1, 2.21.3].
- Can only install one of: nesbot/carbon[1.34.2, 2.21.3].
- Can only install one of: nesbot/carbon[1.34.3, 2.21.3].
- Can only install one of: nesbot/carbon[1.34.4, 2.21.3].
- Can only install one of: nesbot/carbon[1.35.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.35.1, 2.21.3].
- Can only install one of: nesbot/carbon[1.36.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.36.1, 2.21.3].
- Can only install one of: nesbot/carbon[1.36.2, 2.21.3].
- Can only install one of: nesbot/carbon[1.37.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.37.1, 2.21.3].
- Can only install one of: nesbot/carbon[1.38.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.38.1, 2.21.3].
- Can only install one of: nesbot/carbon[1.38.2, 2.21.3].
- Can only install one of: nesbot/carbon[1.38.3, 2.21.3].
- Can only install one of: nesbot/carbon[1.38.4, 2.21.3].
- Can only install one of: nesbot/carbon[1.39.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.21.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.22.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.22.1, 2.21.3].
- Can only install one of: nesbot/carbon[1.23.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.24.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.24.1, 2.21.3].
- Can only install one of: nesbot/carbon[1.24.2, 2.21.3].
- Can only install one of: nesbot/carbon[1.25.0, 2.21.3].
- Can only install one of: nesbot/carbon[1.25.1, 2.21.3].
- Can only install one of: nesbot/carbon[1.25.3, 2.21.3].
- Installation request for nesbot/carbon (locked at 2.21.3) -> satisfiable by nesbot/carbon[2.21.3].

Installation failed, reverting ./composer.json to its original content.