Add message fixture to conftest

[MaayanMashhadi]

Desired Outcome

one fixture of message in conftest and rename the message fixture from saved_message to message,
will make the code more readable.

Implemented Changes

1. message fixture added to conftest.
2. removing the saved_message fixture from message test
3. rename the saved_message fixture to be message.

Connected Issue/Story

Resolves #115
Resolves #106

Dependencies

• This PR does not depend on other PR's

Test coverage

• The changes in this PR do not require tests

Documentation

• This PR does not require updating any documentation

[IdanZimi]

Do you use the message fixture somewhere else beside the message tests? @MaayanMashhadi

[MaayanMashhadi]

Do you use the message fixture somewhere else beside the message tests? @MaayanMashhadi

I don't think so. As I see, the message fixture is only used in the message tests.

[SchSeba]

I think we don't need to move something that is not used by any other test in the project

[amitCohen2]

I think its good convention to do it like that.
But also not necessary if it will not merge for this current demo