Redefine some steps to reflect properly data in the definition

Currently, there are some steps definition that do not clear is the information is data or simple sentence content. Following the Gherkin style, any data should be enclosed with quotation. E.g.

    And  I set header Content-Type to application/ld+json
 
it should be written as

    And  I set header Content-Type to "application/ld+json"
