Secure Sockets Transport Implementation

[diogosilva0307]

Description

• This pull request allows to create sockets with SSL, as well as upload files to the system storage (certificates for example).
• There were added two new options to the CellularSocketOption_t struct as well as another option to the CellularSocketOptionLevel_t struct.
• This was tested with BG96 module.

Checklist:

• I have tested my changes. No regression in existing tests.
• I have modified and/or added unit-tests to cover the code changes in this Pull Request.

Related Issue

#74 [Feature Request] Secure Sockets Transport Implementation
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[chinglee-iot]

Thank you for the PR. I will look into it and discuss with you here.

[chinglee-iot]

@diogosilva0307
Thank you for creating this PR. Besides BG96, we also look into other cellular modems like SARA-R4 and HL7802 specific AT commands to support secure socket connection. We would like to do the following changes base on this PR:

1. Move Cellular_ConfigureSSLContext and Cellular_UploadFileToStorage to port specific layer APIs. The AT commands to configure SSL context and upload credentials is different for cellular modems. Therefore, we would like to move these APIs to a port specific header, for example cellular_bg96_api.h. User who wants to use secure socket connection feature will need to include the port specific header.
2. Move CellularSocketSslConfig_t to port implementation. A pModemData pointer is defined in Cellular socket context for port to extend the socket context. In this way, modem port can define it's own socket specific data without altering the cellular interface.

The PR #147 is created with these changes. We would like to invite you to take a look and feedback in this PR.

[chinglee-iot]

@diogosilva0307
This PR is covered #147
We would like to close this PR due to no response in both PRs.
Feel free to reopen this PRs if you have any updates.