As a violin player myself many years ago, the usual convention is the other way around. String players will follow the slurring as written, usually will only do bow changes when there is no slur. Occasionally performer will do bow changes inside of a slur, but only when needed or when a tenuto/staccato mark indicates that the slur is not really a legato slur. The interpretation of slur+tenuto marks is usually totally different than just a slur only.
The musical phrasing of longer phrases is usually not indicated by slur marks. Usually it's just expected that the performers can get an idea what the musical phrasing should be after playing it a few times, especially when rehearsed together so they understand how all parts together make the overall music.
But as a composer there are still very useful ways to help performers understand the phrasing - by adding subtle clues in the form of words, dynamics or tempo markings, pause breath marks, or stylistic remarks like "dolce". Those hints not only help the composer control how the performers will execute the music, but also gives a chance to hint where phrases end or begin that good performers will subconsciously naturally pick up those clues.
At the same time, don't accidentally overuse those kinds of markings - only use them where you really would want the effect that your asking for.
Hope that helps!