Add PATCH action to plot

[SvenPam]

Add a PATCH action to update beds on a plot.

PATCH /api/allotments/{id}/plot/{id}
Example Body: {
x: 1
y: 1,
bedId: 123456-78910-xxx
}

When this body is sent to the endpoint, the plot service should then work to add the bed to the plot. If a plot is already in that place, every other plot x value should be incremented.

Finally, this updated plot entity needs to be saved via a repository.