[EN][FEAT] Implementação de entrar em grupos na API

[mth-gama]

Title: Entrar em grupos abertos com a API

Detailed Description:

Com o link ou com o id do grupo poderia criar uma rota na api com metodo POST para entrar em um grupo com a instancia criada

Rationale:

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Usage Examples:

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Possible Implementations:

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Impact on the Project:

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Additional Notes:

Any other information you believe is relevant to your request.

[RuanMD]

+1

[leandrosroc]

Confira esse pull request: #373