pass formula as brmsformula

[jsocolar]

Hey @SimonCMills , this is still untested in terms of actually fitting actual models, both via the usual syntax and certainly not via the new bf syntax. However, if it works as intended it should close https://github.com/jsocolar/flocker/issues/70 .

Can you give this one a close look in the next couple of days?

[jsocolar]

This can now hopefully close https://github.com/jsocolar/flocker/issues/69 as well, pending proper testing.

[codecov-commenter]

Codecov Report

Attention: 135 lines in your changes are missing coverage. Please review.

Comparison is base (6685ab1) 38.39% compared to head (7a3cbb7) 37.21%.

:exclamation: Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #71 +/- ## ========================================== - Coverage 38.39% 37.21% -1.18% ========================================== Files 11 11 Lines 2563 2644 +81 ========================================== Hits 984 984 - Misses 1579 1660 +81 ``` | [Files](https://app.codecov.io/gh/jsocolar/flocker/pull/71?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jacob+B.+Socolar) | Coverage Δ | | |---|---|---| | [R/utils.R](https://app.codecov.io/gh/jsocolar/flocker/pull/71?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jacob+B.+Socolar#diff-Ui91dGlscy5S) | `36.50% <3.57%> (-0.30%)` | :arrow_down: | | [R/flock.R](https://app.codecov.io/gh/jsocolar/flocker/pull/71?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jacob+B.+Socolar#diff-Ui9mbG9jay5S) | `0.00% <0.00%> (ø)` | |

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.