Fix documentation warnings

[etorreborre]

Running cargo doc raises many documentation warnings about missing elements. For example:

 /// Create the [`SecureChannel`] [`PurposeKey`]
   |                               ^^^^^^^^^^ no item named `PurposeKey` in scope

We should fix this either by:

• importing the right scope
• or the right element name
• or in some cases not quote a struct name (for example if this is a concrete example of an abstract crate usage)

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[Riahiamirreza]

Would you please assign it to me?

[etorreborre]

Hi @Riahiamirreza please, it's all yours.

[Ankit8848]

@etorreborre Anyone working on it?

[Riahiamirreza]

@Ankit8848 I'm currently working on it.

[Riahiamirreza]

@etorreborre
Hope you're well,
Would guide me on how to resolve this warning? There's not PurposeKey in the code that I can import. The most similar name I could find is PurposeKeys, which I think is not semantically what I'm searching for.

99 |     /// Create the [`SecureChannel`] [`PurposeKey`]
   |                                        ^^^^^^^^^^ no item named `PurposeKey` in scope
   |

[PsychoPunkSage]

Hi @etorreborre
I have created a PR that solves all the warnings that we previously get.
Please have a look at it